Excel 2002 Power Programming with VBA phần 7 pps

To use events with an embed-ded chart, you need to perform the following steps: Create a class module In the VB Editor window, select your project in the Project window and selectInsert

Case xlXErrorBars: Id = “XErrorBars”

Case xlYErrorBars: Id = “YErrorBars”

Case xlLegendEntry: Id = “LegendEntry”

Case xlLegendKey: Id = “LegendKey”

Case xlAxis: Id = “Axis”

Case xlMajorGridlines: Id = “MajorGridlines”

Case xlMinorGridlines: Id = “MinorGridlines”

Case xlAxisTitle: Id = “AxisTitle”

Case xlUpBars: Id = “UpBars”

Case xlDownBars: Id = “DownBars”

Case xlSeriesLines: Id = “SeriesLines”

Case xlHiLoLines: Id = “HiLoLines”

Case xlDropLines: Id = “DropLines”

Case xlRadarAxisLabels: Id = “RadarAxisLabels”

Case xlShape: Id = “Shape”

Case xlNothing: Id = “Nothing”

Case Else: Id = “Some unknown thing”

End SelectMsgBox “Selection type:” & IdEnd Sub

This procedure displays a message box that contains a description of the selecteditem When the Selectevent occurs, the ElementIDargument contains an integerthat corresponds to what was selected The Arg1and Arg2arguments provideadditional information about the selected item (see the online help for details) The

Select Casestructure converts the built-in constants to descriptive strings

Enabling events for an embedded chart

As I noted in the previous section, Chartevents are automatically enabled for chartsheets, but not for charts embedded in a worksheet To use events with an embed-ded chart, you need to perform the following steps:

Create a class module

In the VB Editor window, select your project in the Project window and selectInsert ➪ Class Module This will add a new (empty) class module to your project

If you like, you can use the Properties window to give the class module a moredescriptive name

Declare a public Chart object

The next step is to declare a Publicvariable that will be used as the class name

The variable should be of type Chart, and it must be declared in the class moduleusing the WithEventskeyword If you omit the WithEventskeyword, the objectwill not respond to events Following is an example of such a declaration:

Public WithEvents myChartClass As Chart

Connect the declared object with your chart

Before your event-handler procedures will run, you must connect the declaredobject in the class module with your embedded chart You do this by declaring anobject of type Class1(or whatever your class module is named) This should be amodule-level object variable, declared in a regular VBA module (not in the classmodule) Here’s an example:

Dim MyChart As New MyChartClass

Then you must write code to actually instantiate the object, such as this instruction:

Set myChart.myChartClass = ActiveSheet.ChartObjects(1).Chart

After the preceding statement is executed, the myChartClassobject in the classmodule points to the first embedded chart on the active sheet Consequently, theevent-handler procedures in the class module will execute when the events occur

Write event-handler procedures for the chart class

In this section, I describe how to write event-handler procedures in the class ule Recall that the class module must contain a declaration such as:

mod-Public WithEvents myChartClass As Chart

After this new object has been declared using the WithEventskeyword, it appears

in the Object drop-down list box in the class module When you select the newobject in the Object box, the valid events for that object are listed in the Proceduredrop-down box on the right (see Figure 18-16)

Figure 18-16: The Procedure list displays valid events for the new Chart object.

The following example is a simple event-handler procedure that is executed whenthe embedded chart is activated This procedure simply pops up a message boxthat displays the name of the Chartobject’s parent (which is a ChartObject

object)

Private Sub myChartClass_Activate()MsgBox myChartClass.Parent.Name & “ was activated!”

End SubThe companion CD-ROM contains a workbook that demonstrates the conceptsdescribed in this section

Example: Using Chart events with an embedded chart

The example in this section provides a practical demonstration of the informationpresented in the previous section The example shown in Figure 18-17 consists of anembedded chart that functions as a clickable image map Clicking one of the chartcolumns activates a worksheet that shows detailed data for the region

Figure 18-17: This chart serves as a clickable image map.

The workbook is set up with four worksheets The sheet named Maincontains theembedded chart The other sheets are named North, South, and West Formulas inB1:B4 sum the data in the respective sheets, and this summary data is plotted inthe chart Clicking a column in the chart triggers an event, and the event-handlerprocedure activates the appropriate sheet so the user can view the details for thedesired region

On the CD-ROM

The workbook contains a class module named EmbChartClass, and also a normalVBA module named Module1 For demonstration purposes, the Mainworksheetalso contains two buttons: One executes a procedure named EnableChartEvents,the other executes a procedure named DisableChartEvents(both are located in

Module1) In addition, each of the other worksheets contains a button that cutes the ReturntoMainmacro that reactivates the Mainsheet

exe-The complete listing of Module1 follows:

Dim SummaryChart As New EmbChartClassSub EnableChartEvents()

‘ Called by worksheet buttonRange(“A1”).Select

Set SummaryChart.myChartClass = _Worksheets(1).ChartObjects(1).ChartEnd Sub

Sub DisableChartEvents()

‘ Called by worksheet buttonSet SummaryChart.myChartClass = NothingRange(“A1”).Select

End SubSub ReturnToMain()

‘ Called by worksheet buttonSheets(“Main”).ActivateEnd Sub

The first instruction declares a new object variable SummaryChartto be of type

EmbChartClass— which, as you recall, is the name of the class module When theuser clicks the Enable Chart Events button, the embedded chart is assigned to the

SummaryChartobject, which, in effect, enables the events for the chart Listing 18-4shows the class module for EmbChartClass

Clicking the chart generates a MouseDownevent, which executes the

myChartClass_MouseDownprocedure This procedure uses the GetChartElement

method to determine what element of the chart was clicked The GetChartElement

method returns information about the chart element at specified X and Y nates (information that is available via the arguments for the

coordi-myChartClass_MouseDownprocedure

Listing 18-4: Reacting to which column has been clicked on

Public WithEvents myChartClass As ChartPrivate Sub myChartClass_MouseDown(ByVal Button As Long, _ByVal Shift As Long, ByVal X As Long, ByVal Y As Long)

Dim IDnum As LongDim a As Long, b As Long

‘ The next statement returns values for

‘ IDNum, a, and bmyChartClass.GetChartElement X, Y, IDnum, a, b

‘ Was a series clicked?

If IDnum = xlSeries ThenSelect Case b

Case 1Sheets(“North”).ActivateCase 2

Sheets(“South”).ActivateCase 3

Sheets(“West”).ActivateEnd Select

End IfRange(“A1”).SelectEnd Sub

This workbook is available on the companion CD-ROM

Charting Tricks

I conclude this chapter by sharing a few charting tricks that I’ve discovered overthe years Some of these techniques may be useful in your applications, and othersare simply for fun At the very least, studying them may give you some new insightsinto the object model for charts

Printing embedded charts on a full page

When an embedded chart is selected, you can print the chart by choosing File ➪Print The embedded chart will be printed on a full page by itself (just as if it were

on a chart sheet), yet it will remain an embedded chart

The following macro prints all embedded charts on the active sheet, and each chart

is printed on a full page:

Sub PrintEmbeddedCharts()For Each chtObj In ActiveSheet.ChartObjectschtObj.Chart.Print

Next chtObjEnd Sub

On the CD-ROM

Creating a “dead chart”

Normally, an Excel chart uses data stored in a range Change the data in the range,and the chart is updated automatically In some cases, you may want to “unlink” thechart from its data ranges and produce a “dead chart” (a chart that never changes).For example, if you plot data generated by various what-if scenarios, you may want

to save a chart that represents some baseline so you can compare it with other scenarios

There are two ways to create such a chart:

✦ Paste it as a picture Activate the chart and choose Edit ➪ Copy Then press the

Shift key and select Edit ➪ Paste Picture (the Paste Picture command is able only if you press Shift when you select the Edit menu) The result will be

avail-a picture of the copied chavail-art

✦ Convert the range references to arrays Click on a chart series and then click

the formula bar Press F9 to convert the ranges to an array Repeat this foreach series in the chart

The xl8galry.xls file uses this technique This file is a special workbook used byExcel to store its custom chart formats If you open this workbook, you’ll find 20chart sheets Each chart sheet has “dummy” data, which uses an array rather than

a range as its source

Another way to create a dead chart is to use VBA to assign an array rather than arange to the XValues or Values properties of the Series object

Controlling a data series by hiding data

Figure 18-18 shows a chart that displays daily data for 365 days What if you onlywant to plot, say, the data for February? You could, of course, redefine the chart’sdata range Or, you could take advantage of Excel’s AutoFilter command

By default, a chart does not display data that’s hidden Since Excel’s AutoFilter feature works by hiding rows that don’t meet your criteria, it’s a simple solution.Select Data ➪ Filter ➪ AutoFilter to turn on the AutoFilter mode Each row heading

in the filtered list displays a drop-down arrow Click the arrow and select Customfrom the list Then enter filter criteria that will select the dates that you want toplot The setting shown in Figure 18-19, for example, hides all rows except thosethat have a date in February

Note

Figure 18-18: You can use Excel’s AutoFilter feature to plot only a subset of the data.

This workbook is available on the companion CD-ROM

Figure 18-19: Use the Custom AutoFilter

dialog box to filter a list

The resulting chart is shown in Figure 18-20

On the CD-ROM

Figure 18-20: Only visible cells are displayed in a chart.

If this technique doesn’t seem to be working, you need to change a setting for thechart Activate the chart, then choose Tools ➪ Options In the Options dialog box,click the Chart tab and place a check mark next to Plot visible cells only Also, toensure that the chart doesn’t disappear when its rows are hidden, set its position-ing to Don’t move or size with cells Use the Format ➪ Selected Chart Area com-mand to change this setting

Storing multiple charts on a chart sheet

Most Excel users who take the time to think about it would agree that a chart sheetholds a single chart Most of the time, that’s a true statement However, it’s cer-tainly possible to store multiple charts on a single chart sheet In fact, Excel letsyou do this directly If you activate an embedded chart and then select Chart ➪Location, Excel displays its Chart Location dialog box If you select the As newsheet option and specify an existing chart sheet as the location, the chart willappear on top of the chart in the chart sheet

Most of the time, you’ll want to add embedded charts to an empty chart sheet To

create an empty chart sheet, select a single blank cell and press F11

One advantage of storing multiple charts on a chart sheet is that you can takeadvantage of the View ➪ Sized with Window command to automatically scale thecharts to the window size and dimensions Figure 18-21 shows an example of achart sheet that contains six embedded charts

Note

Figure 18-21: This chart sheet contains six embedded charts.

This workbook is available on the companion CD-ROM

Using linked pictures in a chart

Excel has a feature that lets you display a data table inside of a chart You can selectthis option in Step 3 of the ChartWizard The data table option displays a table thatshows the values used in a chart This is a handy feature, but it’s not very flexible

For example, your formatting options are limited, and you have no control over theposition of the data table (it always appears below the chart)

An alternative to the data table is to use a linked picture of a range Figure 18-22shows an example

On the CD-ROM

Figure 18-22: This chart contains a linked picture of a range used

in the chart

To create a linked picture in a chart, first create the chart as you normally would.Then:

1 Select the range that you would like to include in the chart.

2 Select Edit ➪ Copy.

3 Activate the chart.

4 Press Shift, and then select Edit ➪ Paste Picture This pastes an unlinked

pic-ture of the range

5 To create the link, select the picture and then type a reference to the range in

the formula bar The easiest way to do this is to type an equals sign, and thenreselect the range

The picture now contains a live link to the range If you change the values or cellformatting, they will be reflected in the linked picture

This workbook is available on the companion CD-ROM

On the CD-ROM

Animated charts

Most people don’t realize it, but Excel is capable of performing simple animations

For example, you can animate shapes and charts Consider the XY chart shown inFigure 18-23

Figure 18-23: A simple VBA procedure will turn this graph into an

interesting animation

The X values (column A) depend on the value in cell A1 The value in each row isthe previous row’s value, plus the value in A1 Column B contains formulas thatcalculate the SIN of the corresponding value in column A The following simple procedure produces an interesting animation It simply changes the value in cell A1,which causes the values in the X and Y ranges to change

Sub AnimateChart()Range(“A1”) = 0For i = 1 To 150Range(“A1”) = Range(“A1”) + 0.035Next i

Range(“A1”) = 0End Sub

The companion CD-ROM contains a workbook that includes this animated chart,plus several other animation examples

On the CD-ROM

Creating a hypocycloid chart

Even if you hated your high school trigonometry class, you’ll probably like theexample in this section — which relies heavily on trigonometric functions Theworkbook shown in Figure 18-24 can display an infinite number of dazzling hypocy-cloid curves A hypocycloid curve is the path formed by a point on a circle thatrolls inside of another circle This, as you may recall from your childhood, is thesame technique used in Hasbro’s popular Spirograph toy

Figure 18-24: This workbook generates an infinite number of hypocycloid curves.

This workbook is available on the companion CD-ROM

The chart is an XY chart The X and Y data are generated using formulas stored incolumns A and B The Scrollbar controls at the top let you adjust the three parame-ters that determine the look of the chart These controls are linked to cells B1, B2,and B3 These are controls from the Forms toolbar, and are not ActiveX controls Inaddition, the chart has a Random button that generates random values for thethree parameters

On the CD-ROM

The workbook contains only one macro (which follows), which is executed whenthe Random button is clicked This macro simply generates three random numbersbetween 1 and 250 and inserts them into the worksheet.

Sub Random_Click()RandomizeRange(“B1”) = Int(Rnd * 250)Range(“B2”) = Int(Rnd * 250)Range(“B3”) = Int(Rnd * 250)End Sub

Creating a “clock” chart

Figure 18-25 shows an XY chart formatted to look like a clock It not only looks like a

clock, it also functions as a clock I can’t think of a single reason why anyone wouldneed to display a clock like this on a worksheet, but creating the workbook waschallenging and you may find it instructive

Figure 18-25: This clock is fully functional,

and is actually an XY chart in disguise

This workbook is available on the companion CD-ROM

Besides the clock chart, the workbook contains a text box that displays the time as

a normal string, as shown in Figure 18-26 Normally this is hidden, but it can bedisplayed by deselecting the Analog clock check box

On the CD-ROM

Figure 18-26: Displaying a digital clock in

a worksheet is much easier, but not as fun

to create

As you explore this workbook from the CD-ROM, here are a few things to keep inmind:

✦ The ChartObjectis named ClockChart, and it covers up a range named

DigitalClock, which is used to display the time digitally

✦ The two buttons on the worksheet are from the Forms toolbar, and each has amacro assigned (StartClockand StopClock)

✦ The check box control (named cbClockType) on the worksheet is from theForms toolbar, not from the Control Toolbox toolbar Clicking the object exe-cutes a procedure named cbClockType_Click, which simply toggles the

Visibleproperty of the ChartObject When it’s invisible, the digital clock isrevealed

✦ The chart is an XY chart with four Seriesobjects These series represent thehour hand, the minute hand, the second hand, and the 12 numbers

✦ The UpdateClockprocedure is executed when the Start Clock button isclicked This procedure determines which clock is visible and performs theappropriate updating

✦ The UpdateClockprocedure uses the OnTimemethod of the Application

object This method lets you execute a procedure at a specific time Beforethe UpdateClockprocedure ends, it sets up a new OnTimeevent that willoccur in one second In other words, the UpdateClockprocedure is calledevery second

✦ The UpdateClockprocedure uses some basic trigonometry to determine theangles at which to display the hands on the clock

✦ Unlike most charts, this one does not use any worksheet ranges for its data.Rather, the values are calculated in VBA and transferred directly to the

Valuesand XValuesproperties of the chart’s Seriesobject

Drawing with an XY chart

The final example has absolutely no practical value, but you may find it interesting and maybe even a bit entertaining The worksheet consists of an embedded XY chart,along with a number of controls (these are controls from the Forms toolbar; and arenot ActiveX controls)

This workbook is available on the companion CD-ROM

Clicking one of the arrow buttons draws a line in the chart, the size of which isdetermined by the “step” value, which is set with one of the Spinner controls With

a little practice (and patience), you can create simple sketches Figure 18-27 shows

an example

Figure 18-27: This drawing is actually an embedded XY chart.

Clicking an arrow button executes a macro that adds two values to a range: an Xvalue and a Y value It then redefines two range names (XRangeand YRange) thatare used in the chart’s SERIESformula Particularly handy is the multilevel Undobutton Clicking this button simply erases the last two values in the range, and thenredefines the range names Additional accoutrements include the ability to changethe color of the line, and display “smoothed” lines

On the CD-ROM

Understanding Excel’s Events

In several previous chapters in this book, I presented

exam-ples of VBA “event-handler” procedures An event-handlerprocedure is a specially named procedure that is executedwhen a specific event occurs A simple example is the

CommandButton1_Clickprocedure that is executed whenthe user clicks a CommandButton stored on a UserForm or on

✦ A worksheet is activated or deactivated

✦ Data is entered into a cell, or the cell is edited

✦ A workbook is saved

✦ A worksheet is calculated

✦ An object is clicked

✦ The data in a chart is updated

✦ A particular key or key combination is pressed

✦ A cell is double-clicked

✦ A particular time of day occursThis chapter provides comprehensive coverage of the con-cept of Excel events, and I include many examples that youcan adapt to your own needs As you’ll see, understandingevents can give your Excel applications a powerful edge

19C H A P T E R

In This Chapter

An overview of thetypes of events Excelcan monitor

Essential backgroundinformation forworking with eventsExamples of

Workbookevents,

Worksheetevents,

Chartevents, and

UserFormeventsUsing Application

events to monitor allopen workbooksExamples ofprocessing time-based events andkeystroke events

Event Types That Excel Can Monitor

Excel is programmed to monitor many different events that occur These eventsmay be classified as the following:

✦ Workbook events Events that occur for a particular workbook Examples of

such events include Open(the workbook is opened or created), BeforeSave

(the workbook is about to be saved), and NewSheet(a new sheet is added)

✦ Worksheet events Events that occur for a particular worksheet Examples

include Change(a cell on the sheet is changed), SelectionChange(the usermoves the cell indicator), and Calculate(the worksheet is recalculated)

✦ Chart events Events that occur for a particular chart These events include

Select(an object in the chart is selected) and SeriesChange(a value of adata point in a series is changed) To monitor events for an embedded chart,you use a class module as demonstrated in Chapter 17

✦ Application events Events that occur for the application (Excel) Examples

include NewWorkbook(a new workbook is created), WorkbookBeforeClose

(any workbook is about to be closed), and SheetChange(a cell in any openworkbook is altered) To monitor Application-level events, you need to use

a class module

✦ UserForm events Events that occur for a particular UserForm or an object

contained on the UserForm For example, a UserForm has an Initialize

event (occurs before the UserForm is displayed), and a CommandButton on aUserForm has a Clickevent (occurs when the button is clicked)

✦ Events not associated with objects The final category consists of two useful

Application-level events that I call “On-” events: OnTimeand OnKey Thesework in a different manner than other events

This chapter is organized according to the preceding list Within each section, I provide examples to demonstrate some of the events

What You Should Know about Events

This section provides some essential information relevant to working with eventsand writing event-handler procedures

Understanding event sequences

As you’ll see, some actions trigger multiple events For example, when you insert anew worksheet into a workbook, this action triggers three Application-levelevents:

✦WorkbookNewSheet: Occurs when a new worksheet is added.

✦SheetDeactivateevent: Occurs when the active worksheet is deactivated

✦SheetActivateevent: Occurs when the newly added worksheet is activated

Event sequencing is a bit more complicated than you might think The eventslisted above are Application-level events When adding a new worksheet, addi-tional events occur at the Workbook level and at the Worksheet level

At this point, just keep in mind that events fire in a particular sequence, and ing what the sequence is can be critical when writing event-handler procedures

know-Later in this chapter, I describe how to determine the order of the events that occurfor a particular action (see “Monitoring Application-level events”)

Where to put event-handler procedures

VBA newcomers often wonder why their event-handler procedures aren’t being cuted when the corresponding event occurs The answer is almost always becausethese procedures are located in the wrong place

exe-In the VB Editor window, each project is listed in the Projects window The projectcomponents are arranged in a collapsible list, as shown in Figure 19-1

Figure 19-1: The components for each VBA

Project are listed in the Project window

Each of the following components has its own code module:

✦Sheetobjects (for example, Sheet1, Sheet2, and so on)

✦Chartobjects (that is, chart sheets)

✦ThisWorkbookobject

Note

✦ General VBA modules You never put event-handler procedures in a general(that is, nonobject) module.

✦ Class modules

Even though the event-handler procedure must be located in the correct module,the procedure can call other standard procedures stored in other modules Forexample, the following event-handler procedure, located in the module for the

ThisWorkbookobject, calls a procedure named WorkbookSetup,which could bestored in a regular VBA module:

Private Sub Workbook_Open()Call WorkbookSetupEnd Sub

Disabling events does not apply to events triggered by UserForm controls — for

example, the Click event generated by clicking a CommandButton control on aUserForm

Why would you need to disable events? The main reason is to prevent an infiniteloop of cascading events

For example, suppose that cell A1 of your worksheet must always contain a valueless than or equal to 12 You can write some code that is executed whenever data isentered into a cell to validate the cell’s contents In this case, you are monitoringthe Changeevent for a Worksheetusing a procedure named Worksheet_Change.Your procedure checks the user’s entry, and if the entry isn’t less than or equal to

12, it displays a message and then clears that entry The problem is, clearing theentry with your VBA code generates a new Changeevent, so your event-handlerprocedure is executed again This is not what you want to happen, so you need todisable events before you clear the cell, and then enable events again so you canmonitor the user’s next entry

Another way to prevent an infinite loop of cascading events is to declare a StaticBoolean variable at the beginning of your event-handler procedure, such as this:

Static AbortProc As Boolean

Note

Whenever the procedure needs to make its own changes, set the AbortProcable to True (otherwise, make sure it is set to False) Insert the following code atthe top of the procedure:

vari-If AbortProc Then AbortProc = FalseExit Sub

Caution

Cross-Reference

Programming Events in Older Versions of Excel

Versions of Excel prior to Office 97 also supported events, but the programming techniquesrequired to take advantage of those were quite different from those described in this chapter

For example, if you have a procedure named Auto_Openstored in a regular VBA module,this procedure will be executed when the workbook is opened Beginning with Excel 97,the Auto_Openprocedure is supplemented by the Workbook_Openevent-handler proce-dure, stored in the code module for the ThisWorkbook object, and executed prior to

Auto_Open.Before Excel 97, it was often necessary to explicitly set up events For example, if youneeded to execute a procedure whenever data was entered into a cell, you would need toexecute a statement such as:

Sheets(“Sheet1”).OnEntry = “ValidateEntry”

This statement instructs Excel to execute the procedure named ValidateEntrywheneverdata is entered into a cell With Excel 97 and later, you simply create a procedure named

Worksheet_Changeand store it in the code module for the Sheet1object

For compatibility reasons, Excel 97 and later versions still support the older event nism (although they no longer are documented in the online help system) If you’re devel-oping applications that will be used only with Excel 97 or later, you’ll definitely want to usethe techniques described in this chapter

mecha-Entering event-handler code

Every event-handler procedure has a predetermined name Following are someexamples of event-handler procedure names:

Worksheet_SelectionChangeWorkbook_Open

Chart_ActivateClass_Initialize

You can declare the procedure by typing it manually, but a much better approach is

to let the VB Editor do it for you

Figure 19-2 shows the code module for the ThisWorkbookobject To insert a dure declaration, select Workbookfrom the objects list on the left Then select theevent from the procedures list on the right When you do so, you’ll get a procedure

proce-“shell” that contains the procedure declaration line and an End Substatement

Figure 19-2: The best way to create an event procedure is

to let the VB Editor do it for you

For example, if you select Workbookfrom the objects list and Openfrom the dures list, the VB Editor will insert the following (empty) procedure:

proce-Private Sub Workbook_Open()End Sub

Your code, of course, goes between these two statements

Event-handler procedures that use arguments

Some event-handler procedures use an argument list For example, you may need tocreate an event-handler procedure to monitor the SheetActivateevent for a work-book If you use the technique described in the previous section, the VB Editor willcreate the following procedure:

Private Sub Workbook_SheetActivate(ByVal Sh As Object)End Sub

This procedure uses one argument (Sh), which represents the sheet that was vated In this case, Shis declared as an Objectdatatype rather than a Worksheet

acti-datatype That’s because the activated sheet can also be a chart sheet

Your code can, of course, make use of the data passed as an argument The ing procedure is executed whenever a sheet is activated It displays the type andname of the activated sheet by using VBA’s TypeNamefunction and accessing the

follow-Nameproperty of the object passed in the argument:

Private Sub Workbook_SheetActivate(ByVal Sh As Object)MsgBox TypeName(Sh) & vbCrLf & Sh.Name

End Sub

Several event-handler procedures use a Booleanargument named Cancel Forexample, the declaration for a workbook’s BeforePrintevent is as follows:

Private Sub Workbook_BeforePrint(Cancel As Boolean)

The value of Cancelpassed to the procedure is False However, your code cansetCancelto True, which will cancel the printing The following exampledemonstrates:

Private Sub Workbook_BeforePrint(Cancel As Boolean)Msg = “Have you loaded the 5164 label stock?”

Ans = MsgBox(Msg, vbYesNo, “About to print ”)

If Ans = vbNo Then Cancel = TrueEnd Sub

The Workbook_BeforePrintprocedure is executed before the workbook isprinted This routine displays the message box shown in Figure 19-3 If the userclicks the No button, Cancelis set to True and nothing is printed

The BeforePrint event also occurs when the user previews a worksheet

Note

Figure 19-3: You can cancel the print operation by changing

the Cancelargument

Unfortunately, Excel does not provide a sheet-level BeforePrintevent Therefore,your code cannot determine what is about to be printed

Event Action that triggers the event

Activate A workbook is activated.

AddinInstall A workbook is installed as an add-in.

AddinUninstall A workbook is uninstalled as an add-in.

BeforeClose A workbook is about to be closed.

BeforePrint A workbook (or anything in it) is about to be printed

or previewed.

BeforeSave A workbook is about to be saved.

Deactivate A workbook is deactivated.

NewSheet A new sheet is created in a workbook.

Open A workbook is opened.

PivotTableCloseConnection* An external data source connection for a pivot table

is closed.

PivotTableOpenConnection* An external data source connection for a pivot table

is opened.

SheetActivate Any sheet is activated.

SheetBeforeDoubleClick Any worksheet is double-clicked This event occurs

before the default double-click action.

Event Action that triggers the event

SheetBeforeRightClick Any worksheet is right-clicked This event occurs

before the default right-click action.

SheetCalculate Any worksheet is calculated (or recalculated).

SheetChange Any worksheet is changed by the user or by an

external link.

SheetDeactivate Any sheet is deactivated.

SheetFollowHyperlink A hyperlink on a sheet is clicked.

SheetPivotTableUpdate* A pivot table is updated with new data.

SheetSelectionChange The selection on any worksheet is changed.

WindowActivate Any workbook window is activated.

WindowDeactivate Any workbook window is deactivated.

WindowResize Any workbook window is resized.

* These events occur only in Excel 2002, and are not supported in previous versions.

If you need to monitor events for any workbook, you need to work with

Application-level events (see “Application Events,” later in this chapter)

The remainder of this section presents examples of using Workbook-levelevents All of the example procedures that follow must be located in thecode module for the ThisWorkbookobject If you put them into any othertype of code module, they won’t work

The Open event

One of the most common events that is monitored is the Openevent for a book This event is triggered when the workbook (or add-in) is opened, and exe-cutes the Workbook_Openprocedure A Workbook_Openprocedure can do almostanything, and often is used for tasks such as:

work-✦ Displaying welcome messages

✦ Opening other workbooks

✦ Setting up custom menus or toolbars

✦ Activating a particular sheet or cell

✦ Ensuring that certain conditions are met For example, a workbook mayrequire that a particular add-in is installed

✦ Setting up certain automatic features For example, you can define key nations (see “The OnKeyevent” later in this chapter)

combi-

Cross-Reference

✦ Setting a worksheet’s ScrollAreaproperty (which isn’t stored with theworkbook).

✦ Setting UserInterfaceOnlyprotection for worksheets, so your code canoperate on protected sheets This setting is an argument for the Protect

method and is not stored with the workbook

If the user holds down the Shift key when opening a workbook, the workbook’sWorkbook_Openprocedure will not execute

Following is a simple example of a Workbook_Openprocedure It uses VBA’s

Weekdayfunction to determine the day of the week If it’s Friday, a message boxappears, reminding the user to perform a weekly file backup If it’s not Friday, nothing happens

Private Sub Workbook_Open()

If Weekday(Now) = vbFriday ThenMsg = “Today is Friday Make sure that you “Msg = Msg & “do your weekly backup!”

MsgBox Msg, vbInformationEnd If

End Sub

The Activate event

The following procedure is executed whenever the workbook is activated This procedure simply maximizes the active window

Private Sub Workbook_Activate()ActiveWindow.WindowState = xlMaximizedEnd Sub

The SheetActivate event

The following procedure is executed whenever the user activates any sheet in theworkbook If the sheet is a worksheet, the code simply selects cell A1 If the sheet isnot a worksheet, nothing happens This procedure uses VBA’s TypeNamefunction toensure that the activated sheet is a worksheet (as opposed to a chart sheet)

Private Sub Workbook_SheetActivate(ByVal Sh As Object)

If TypeName(Sh) = “Worksheet” Then _Range(“A1”).Select

End Sub

An alternative method to avoid the error that occurs when you try to select a cell

on a chart sheet is to simply ignore the error

Caution

Private Sub Workbook_SheetActivate(ByVal Sh As Object)

On Error Resume NextRange(“A1”).SelectEnd Sub

The NewSheet event

The following procedure is executed whenever a new sheet is added to the book The sheet is passed to the procedure as an argument Since a new sheet can

work-be either a worksheet or a chart sheet, this procedure determines the sheet type Ifit’s a worksheet, the code inserts a date and time stamp in cell A1

Private Sub Workbook_NewSheet(ByVal Sh As Object)

If TypeName(Sh) = “Worksheet” Then _Range(“A1”) = “Sheet added “ & Now()End Sub

The BeforeSave event

The BeforeSaveevent occurs before the workbook is actually saved As you know,using the File ➪ Save command sometimes brings up the Save As dialog box Thishappens if the workbook has never been saved, or if it was opened in read-onlymode

When the Workbook_BeforeSaveprocedure is executed, it receives an argument(SaveAsUI) that lets you identify if the Save As dialog box will be displayed Thefollowing example demonstrates:

Private Sub Workbook_BeforeSave _(ByVal SaveAsUI As Boolean, Cancel As Boolean)

If SaveAsUI ThenMsgBox “Click OK to display the Save As dialog box.”

End IfEnd Sub

When the user attempts to save the workbook, the Workbook_BeforeSavedure is executed If the save operation will bring up Excel’s Save As dialog box, the

proce-SaveAsUIvariable is True The procedure above checks this variable and displays

a message only if the Save As dialog box will be displayed If the procedure sets the

Cancelargument to True, the file will not be saved

The Deactivate event

The following example demonstrates the Deactivateevent This procedure is cuted whenever the workbook is deactivated, and essentially never lets the userdeactivate the workbook When the Deactivateevent occurs, the code re-activatesthe workbook and displays a message

exe-Private Sub Workbook_Deactivate()Me.Windows(1).Activate

MsgBox “Sorry, you may not leave this workbook”

End Sub

I do not recommend using procedures — such as this one — that attempt to “takeover” Excel It can be very frustrating and confusing for the user Rather, I wouldrecommend training the user how to use your application correctly

This simple example illustrates the importance of understanding event sequences

If you try out this procedure, you’ll see that it works well if the user attempts toactivate another workbook However, it’s important to understand that the work-book Deactivateevent is also triggered by the following actions:

✦ Closing the workbook

✦ Opening a new workbook

✦ Minimizing the workbook

In other words, this procedure may not perform as it was originally intended Itdoes prevent the user from activating a different workbook directly, but he or shecan close the workbook, open a new one, or minimize the workbook The messagebox will still appear, but the actions will occur anyway

The BeforePrint event

The BeforePrintevent occurs when the user requests a print or a print preview,but before the printing or previewing actually occurs The event uses a Cancel

argument, so your code can cancel the printing or previewing by setting the Cancel

variable to True Unfortunately, there is no way to determine if the BeforePrint

event was triggered by a print request or a preview request

Before Excel 2002, users were often dismayed to discover that it was not possible

to print a workbook’s full path in the page header or footer Excel 2002 solves thisproblem by adding a new option to the Header and Footer dialog boxes (accessedfrom the Page Setup dialog box)

If you’re still using an older version of Excel, the only solution is to write code thatinserts the workbook’s path into the header or footer The Workbook_BeforePrint

event is perfect for this The following code demonstrates:

Private Sub Workbook_BeforePrint(Cancel As Boolean)For Each sht In ThisWorkbook.Sheets

This procedure loops through each sheet in the workbook and sets the LeftFooter

property of the PageSetupobject to the FullNameproperty of the workbook(which is the filename and path) It also sets the font size to 8 points

This example exposes an inconsistency in Excel’s object model To change the fontsize of header or footer text, you must use a string that contains a special format-ting code In the example above, “&8” is the code for 8-point font Ideally, thereshould be a Font object available for page headers and footers To find out theother formatting codes available, consult the online help (or record a macro whileyou access the Page Setup dialog box)

When testing BeforePrint event-handlers, you can save time (and paper) bypreviewing rather than actually printing

The BeforeClose event

The BeforeCloseevent occurs before a workbook is closed This event is oftenused in conjunction with a Workbook_Openevent-handler For example, you mightuse the Workbook_Openprocedure to create a custom menu for your workbook,and then use the Workbook_BeforeCloseprocedure to delete the custom menuwhen the workbook is closed That way, the custom menu is available only whenthe workbook is open

As you know, if you attempt to close a workbook that hasn’t been saved, Excel plays a prompt asking if you want to save the workbook before closing, as shown inFigure 19-4

dis-Figure 19-4: When this message appears,

Workbook_BeforeClosehas already done its thing

A potential problem can arise because by the time the user sees this message, theBeforeClose event has already occurred — which means that yourWorkbook_BeforeCloseprocedure has already executed

Consider this scenario: You need to display a custom menu when a particular book is open Therefore, your workbook uses a Workbook_Openprocedure to cre-ate the menu when the workbook is opened, and it uses a Workbook_BeforeClose

work-procedure to remove the menu when the workbook is closed These two handler procedures follow Both of these call other procedures, which are notshown here

event-Caution Tip Note

Private Sub Workbook_Open()Call CreateMenu

End SubPrivate Sub Workbook_BeforeClose(Cancel As Boolean)Call DeleteMenu

End Sub

As I noted above, Excel’s “Do you want to save ” prompt occurs after the

Workbook_BeforeCloseevent-handler runs So if the user clicks Cancel, the book remains open, but the custom menu item has already been deleted!

work-One solution to this problem is to bypass Excel’s prompt and write your own code

in the Workbook_BeforeCloseprocedure to ask the user to save the workbook.The following code demonstrates:

Private Sub Workbook_BeforeClose(Cancel As Boolean)Dim Msg As String

If Me.Saved ThenCall DeleteMenuExit Sub

ElseMsg = “Do you want to save the changes you made to “Msg = Msg & Me.Name & “?”

Ans = MsgBox(Msg, vbQuestion + vbYesNoCancel)Select Case Ans

Case vbYesMe.SaveCall DeleteMenuCase vbNo

Me.Saved = TrueCall DeleteMenuCase vbCancelCancel = TrueEnd Select

End IfEnd Sub

This procedure checks the Savedproperty of the Workbookobject to determine ifthe workbook has been saved If so, no problem — the DeleteMenuprocedure isexecuted and the workbook is closed But if the workbook has not been saved, theprocedure displays a message box that duplicates the one that Excel would nor-mally show If the user clicks Yes, the workbook is saved, the menu is deleted, andthe workbook is closed If the user clicks No, the code sets the Savedproperty ofthe Workbookobject to True (but doesn’t actually save the file), and deletes themenu If the user clicks Cancel, the BeforeCloseevent is canceled and the proce-dure ends without deleting the menu

Event Action that triggers the event

Activate The worksheet is activated.

BeforeDoubleClick The worksheet is double-clicked.

BeforeRightClick The worksheet is right-clicked.

Calculate The worksheet is calculated (or recalculated).

Change Cells on the worksheet are changed by the user or by an

external link.

Deactivate The worksheet is deactivated.

FollowHyperlink A hyperlink on the sheet is clicked.

PivotTableUpdate* A pivot table on the sheet is updated.

SelectionChange The selection on the worksheet is changed.

* This event occurs only in Excel 2002, and is not supported in previous versions.

Remember that the code for a worksheet event must be stored in the code modulefor the specific worksheet

To quickly activate the code module for a worksheet, right-click the sheet tab, andchoose View Code

The Change event

The Changeevent is triggered when any cell in a worksheet is changed by the user

or by an external link The Changeevent is not triggered when a calculation ates a different value for a formula, or when an object is added to the sheet

gener-Tip Note

When the Worksheet_Changeprocedure is executed, it receives a Rangeobject asits Targetargument This Rangeobject represents the changed cell or range thattriggered the event The following example displays a message box that shows theaddress of the Targetrange:

Private Sub Worksheet_Change(ByVal Target As Excel.Range)MsgBox “Range “ & Target.Address & “ was changed.”

End Sub

To get a better feel for the types of actions that generate a Changeevent for a sheet, enter the preceding procedure in the code module for a Worksheetobject.After entering this procedure, activate Excel and make some changes to the work-sheet using various techniques Every time the Changeevent occurs, you’ll see amessage box that displays the address of the range that was changed

work-When I ran this procedure, I discovered some interesting quirks Some actions thatshould trigger the event don’t, and other actions that should not trigger the event do!

✦ Changing the formatting of a cell does not trigger the Changeevent (as

expected), but using the Edit ➪ Clear Formats command does trigger the

event

✦ Adding, editing, or deleting a cell comment does not trigger the Changeevent

✦ Pressing Del generates an event even if the cell is empty to start with

✦ Cells that are changed by using Excel commands may or may not trigger the

Changeevent For example, the Data ➪ Form command and the Data ➪ Sortcommand do not trigger the event But the Tools ➪ Spelling command and theEdit ➪ Replace command do trigger the Changeevent

✦ If your VBA procedure changes a cell, it does trigger the Changeevent

As you can see from the preceding list, it’s not a good idea to rely on the Change

event to detect cell changes for critical applications

To add to the confusion, triggers for the Change event vary, depending on the sion of Excel For versions earlier than Excel 2002, filling a range using the Edit ➪Fill command does not generate a Change event Nor does using the Edit ➪Delete command to delete cells

ver-Monitoring a specific range for changes

The Changeevent occurs when any cell on the worksheet is changed But in mostcases all you care about are changes made to a specific cell or range When the

Worksheet_Changeevent-handler procedure is called, it receives a Rangeobject

as its argument This Rangeobject represents the cell or cells that were changed

Note

Assume that your worksheet has a range named InputRange, and you would like tomonitor changes made only within this range There is no Changeevent for a Range

object, but you can perform a quick check within the Worksheet_Changedure The following procedure demonstrates:

proce-Private Sub Worksheet_Change(ByVal Target As Excel.Range)Dim VRange As Range

Set VRange = Range(“InputRange”)

If Not Intersect(Target, VRange) Is Nothing Then _MsgBox “A changed cell is in the input range.”

End Sub

This example uses a Rangeobject variable named VRange, which represents theworksheet range that you are interested in monitoring for changes The procedureuses VBA’s Intersectfunction to determine if the Targetrange (passed to theprocedure in its argument) is contained in VRange The Intersectfunction returns

an object that consists of all the cells that are contained in both of its arguments Ifthe Intersectfunction returns Nothing, then the ranges have no cells in common

The Notoperator is used so the expression returns Trueif the ranges do have at

least one cell in common Therefore, if the changed range has any cells in commonwith the range named InputRange, a message box is displayed Otherwise, the procedure ends and nothing happens

Tracking cell changes in a comment

The following example adds a notation to the cell’s comment each time the cell ischanged (as determined by the Changeevent) The state of a CheckBox, embedded

on the worksheet, determines if the change is added to the comment Figure 19-5shows an example of a comment for a cell that has been changed several times

Figure 19-5: The Worksheet_Changeprocedure appends the comment with each cell change

This example is available on the companion CD-ROM.

Private Sub Worksheet_Change(ByVal Target As Excel.Range)

If CheckBox1 ThenFor Each cell In TargetWith cell

On Error Resume NextOldText = Comment.Text

If Err <> 0 Then AddCommentNewText = OldText & “Changed to “ & cell.Text & _

“ by “ & Application.UserName & “ at “ & Now &vbLf

.Comment.Text NewText.Comment.Visible = True.Comment.Shape.SelectSelection.AutoSize = True.Comment.Visible = FalseEnd With

Next cellEnd IfEnd Sub

Because the object passed to the Worksheet_Changeprocedure can consist of amulticell range, the procedure loops through each cell in the Targetrange If thecell doesn’t already contain a comment, one is added Then new text is appended tothe existing comment text (if any)

This example is primarily for instructional purposes If you really need to trackchanges in a worksheet, Excel’s Tools ➪ Track Changes feature does a much better job

Validating data entry

Excel’s Data Validation feature is a useful tool, but it suffers from a potentially ous problem When you paste data to a cell that uses data validation, the pastedvalue not only fails to get validated, it also deletes the validation rules associatedwith the cell! This fact makes the Data Validation feature practically worthless forcritical applications In this section, I demonstrate how you can make use of the

seri-Changeevent for a worksheet to create your own data validation procedure

The companion CD-ROM contains two versions of this example One uses theEnableEventsproperty to prevent cascading Change events, the other uses aStatic variable (see “Disabling events,” earlier in this chapter)

Listing 19-1 presents a procedure that is executed when a cell is changed by theuser The validation is restricted to the range named InputRange Values enteredinto this range must be integers between 1 and 12

On the CD-ROM Note

On the CD-ROM

Listing 19-1: Determining whether a cell entry

is to be validated

Private Sub Worksheet_Change(ByVal Target As Excel.Range)Dim VRange As Range, cell As Range

Dim Msg As StringDim ValidateCode As VariantSet VRange = Range(“InputRange”)For Each cell In Target

If Union(cell, VRange).Address = VRange.Address ThenValidateCode = EntryIsValid(cell)

If ValidateCode = True ThenExit Sub

ElseMsg = “Cell “ & cell.Address(False, False) _

& “:”

Msg = Msg & vbCrLf & vbCrLf & ValidateCodeMsgBox Msg, vbCritical, “Invalid Entry”

Application.EnableEvents = Falsecell.ClearContents

cell.ActivateApplication.EnableEvents = TrueEnd If

End IfNext cellEnd Sub

The Worksheet_Changeprocedure creates a Range object (named VRange) thatrepresents the worksheet range that is validated Then it loops through each cell

in the Targetargument, which represents the cell or cells that were changed Thecode determines if each cell is contained in the range to be validated If so, it passesthe cell as an argument to a custom function (EntryIsValid), which returns True ifthe cell is a valid entry

If the entry is not valid, the EntryIsValidfunction returns a string that describesthe problem, and the user is informed via a message box (see Figure 19-6) Whenthe message box is dismissed, the invalid entry is cleared from the cell and the cell

is activated Notice that events are disabled before the cell is cleared If events werenot disabled, clearing the cell would produce a Changeevent that causes an end-less loop

Figure 19-6: This message box describes the problem

when the user makes an invalid entry

The EntryIsValidfunction procedure is presented in Listing 19-2.

Listing 19-2: Validating an entry just made

into a restricted range

Private Function EntryIsValid(cell) As Variant

‘ Returns True if cell is an integer between 1 and 12

‘ Otherwise it returns a string that describes the problem

‘ Numeric?

If Not WorksheetFunction.IsNumber (cell) ThenEntryIsValid = “Non-numeric entry.”

Exit FunctionEnd If

‘ Integer?

If CInt(cell) <> cell ThenEntryIsValid = “Integer required.”

Exit FunctionEnd If

‘ Between 1 and 12?

If cell < 1 Or cell > 12 ThenEntryIsValid = “Valid values are between 1 and 12.”Exit Function

End If

‘ It passed all the testsEntryIsValid = TrueEnd Function

The SelectionChange event

The following procedure demonstrates the SelectionChangeevent It’s executedwhenever the user makes a new selection on the worksheet

Private Sub Worksheet_SelectionChange(ByVal Target _

As Excel.Range)Cells.Interior.ColorIndex = xlNoneWith ActiveCell

.EntireRow.Interior.ColorIndex = 36.EntireColumn.Interior.ColorIndex = 36End With

End Sub

This procedure shades the row and column of the active cell, which makes it veryeasy to identify the active cell The first statement removes the background colorfor all cells in the worksheet Next, the entire row and column of the active cell isshaded light yellow Figure 19-7 shows the shading in effect; trust me, it’s yellow

Figure 19-7: Moving the cell cursor causes the active cell’s row and column

to be shaded

This example is available on the companion CD-ROM

You won’t want to use the procedure if your worksheet contains backgroundshading, because it will be wiped out

The BeforeRightClick event

When the user right-clicks in a worksheet, Excel displays a shortcut menu If, forsome reason, you’d like to prevent the shortcut menu from appearing in a particu-lar sheet, you can trap the RightClickevent The following procedure sets the

Cancelargument to True, which cancels the RightClickevent and thereby cancels the shortcut menu Instead, a message box is displayed

Private Sub Worksheet_BeforeRightClick _(ByVal Target As Excel.Range, Cancel As Boolean)Cancel = True

MsgBox “The shortcut menu is not available.”

End SubChapter 24 describes other methods to disable shortcut menus

Cross-Reference

Caution

On the CD-ROM

Events Recognized by a Chart Sheet

Event Action that triggers the event

Activate The chart sheet or embedded chart is activated.

BeforeDoubleClick The chart sheet or an embedded chart is double-clicked This

event occurs before the default double-click action.

BeforeRightClick The chart sheet or an embedded chart is right-clicked The event

occurs before the default right-click action.

Calculate New or changed data is plotted on a chart.

Deactivate The chart is deactivated.

DragOver A range of cells is dragged over a chart.

DragPlot A range of cells is dragged and dropped onto a chart.

MouseDown A mouse button is pressed while the pointer is over a chart MouseMove The position of the mouse pointer changes over a chart.

MouseUp A mouse button is released while the pointer is over a chart Resize The chart is resized.

Select A chart element is selected.

SeriesChange The value of a chart data point is changed.

Application Events

In previous sections, I discussed Workbookevents and Worksheetevents Thoseevents are monitored for a particular workbook If you would like to monitor eventsfor all open workbooks or all worksheets, you use Applicationlevel events

Cross-Reference

Using the Object Browser to Locate Events

The Object Browser is a useful tool that can help you learn about objects and their ties and methods It can also help you find out which objects support a particular event Forexample, say you’d like to find out which objects support the MouseMoveevent Activate the

proper-VB Editor and press F2 to display the Object Browser window Make sure <All Libraries> is

selected and then type MouseMove and click the binoculars icon (see the accompanying

as that for another belonging to a different library or class — although they probably do notshare the same functionality So be sure to click each item in the Object Browser list andcheck the status bar at the bottom of the list for the syntax You might find, for instance, thatone class or library treats an event differently

Creating event-handler procedures to handle Application events alwaysrequires a class module and some set-up work.

Table 19-4 lists the Applicationevents, with a brief description of each

Table 19-4

Events Recognized by the Application Object

Event Action that triggers the event

NewWorkbook A new workbook is created.

SheetActivate Any sheet is activated.

SheetBeforeDoubleClick Any worksheet is double-clicked This event occurs

before the default double-click action.

SheetBeforeRightClick Any worksheet is right-clicked This event occurs before

the default right-click action.

SheetCalculate Any worksheet is calculated (or recalculated).

SheetChange Cells in any worksheet are changed by the user or by an

external link.

SheetDeactivate Any sheet is deactivated.

SheetFollowHyperlink A hyperlink is clicked.

SheetPivotTableUpdate* Any pivot table is updated.

SheetSelectionChange The selection changes on any worksheet except a chart

sheet.

WindowActivate Any workbook window is activated.

WindowDeactivate Any workbook window is deactivated.

WindowResize Any workbook window is resized.

WorkbookActivate Any workbook is activated.

WorkbookAddinInstall A workbook is installed as an add-in.

WorkbookAddinUninstall Any add-in workbook is uninstalled.

WorkbookBeforeClose Any open workbook is closed.

WorkbookBeforePrint Any open workbook is printed.

WorkbookBeforeSave Any open workbook is saved.

WorkbookDeactivate Any open workbook is deactivated.

WorkbookNewSheet A new sheet is created in any open workbook.

Note