Using the Open event

One of the most common monitored events is a workbook's Open event. This event is triggered when the workbook opens and executes the Workbook_Open procedure. A Workbook_Open procedure is versatile, and it is often used for the following tasks:

• Displaying welcome messages
• Opening other workbooks
• Activating a specific sheet
• Ensuring that certain conditions are met; for example, a workbook may require that a particular add-in is installed

The following is a simple example of a Workbook_Open procedure. It uses the VBA Weekday function to determine the day of the week. If it's Friday, a message box appears to remind the user to perform a file backup. If it's not Friday, nothing happens.

Private Sub Workbook_Open()
   If Weekday(Now) = 6 Then
      Msg = "Make sure you do your weekly backup!"
      MsgBox Msg, vbInformation
  End If
End Sub 

The following example performs a number of actions when the workbook is opened. It maximizes the workbook window, activates the sheet named DataEntry, selects the first empty cell in column A, and enters the current date into that cell. If a sheet named DataEntry does not exist, the code generates an error.

Private Sub Workbook_Open()
   ActiveWindow.WindowState = xlMaximized
   Worksheets("DataEntry").Activate
   Range("A1").End(xlDown).Offset(1,0).Select
   ActiveCell.Value = Date
End Sub 

Using the SheetActivate event

The following procedure executes whenever the user activates a sheet in the workbook. The code simply selects cell A1. Including the On Error Resume Next statement causes the procedure to ignore the error that occurs if the activated sheet is a chart sheet:

Private Sub Workbook_SheetActivate(ByVal Sh As Object)
   On Error Resume Next
   Range("A1").Select
End Sub 

An alternative method to handle the case of a chart sheet is to check the sheet type. Use the Sh argument, which is passed to the procedure:

Private Sub Workbook_SheetActivate(ByVal Sh As Object)
   If TypeName(Sh) = "Worksheet" Then Range("A1").Select
End Sub 

Using the NewSheet event

The following procedure executes whenever a new sheet is added to the workbook. The sheet is passed to the procedure as an argument. Because a new sheet can be either a worksheet or a chart sheet, this procedure determines the sheet type. If it's a worksheet, it inserts a date and time stamp in cell A1:

Private Sub Workbook_NewSheet(ByVal Sh As Object)
  If TypeName(Sh) = "Worksheet" Then _
    Sh.Range("A1").Value = "Sheet added " & Now()
End Sub 

Using the BeforeSave event

The BeforeSave event occurs before the workbook is actually saved. As you know, choosing File ⇨ Save sometimes brings up the Save As dialog box—for example, when the file has never been saved or was opened in read-only mode.

When the Workbook_BeforeSave procedure executes, it receives an argument that enables you to identify whether the Save As dialog box will appear. The following example demonstrates this:

Private Sub Workbook_BeforeSave _
 (ByVal SaveAsUI As Boolean, Cancel As Boolean)
    If SaveAsUI Then
       MsgBox "Use the new file-naming convention."
    End If
End Sub 

When the user attempts to save the workbook, the Workbook_BeforeSave procedure executes. If the save operation brings up the Save As dialog box, the SaveAsUI variable is True. The preceding procedure checks this variable and displays a message only if the Save As dialog box is displayed. In this case, the message is a reminder about how to name the file.

The BeforeSave event procedure also has a Cancel variable in its argument list. If the procedure sets the Cancel argument to True, the file is not saved.

Using the BeforeClose event

The BeforeClose event occurs before a workbook is closed. This event is often used in conjunction with a Workbook_Open event handler. For example, use the Workbook_Open procedure to initialize items in your workbook, and use the Workbook_BeforeClose procedure to clean up or restore settings to normal before the workbook closes.

If you attempt to close a workbook that hasn't been saved, Excel displays a prompt that asks whether you want to save the workbook before it closes.

Using the Change event

A Change event is triggered when a user changes any cell in the worksheet. A Change event is not triggered when a calculation generates a different value for a formula or when an object (such as a chart or a shape) is added to the sheet.

When the Worksheet_Change procedure executes, it receives a Range object as its Target argument. This Range object corresponds to the changed cell or range that triggered the event. The following example displays a message box that shows the address of the Target range:

Private Sub Worksheet_Change(ByVal Target As Range)
    MsgBox "Range " & Target.Address & " was changed."
End Sub 

To get a feel for the types of actions that generate the Change event for a worksheet, enter the preceding procedure into the code module for a Worksheet object. After you enter this procedure, activate Excel and, using various techniques, make changes to the worksheet. Every time the Change event occurs, a message box displays the address of the range that changed.

Unfortunately, the Change event doesn't always work as expected. For example,

• Changing the formatting of a cell does not trigger the Change event (as expected), but choosing Home ⇨ Editing ⇨ Clear ⇨ Clear Formats does.
• Pressing Delete generates an event even if the cell is empty at the start.
• Cells changed via Excel commands may or may not trigger the Change event. For example, sorting and goal-seeking operations do not trigger the Change event. However, operations such as Find and Replace, using the AutoSum button, or adding a Total row to a table do trigger the event.
• If your VBA procedure changes a cell, it does trigger the Change event.

Monitoring a specific range for changes

Although the Change event occurs when any cell on the worksheet changes, most of the time you'll be concerned only with changes that are made to a specific cell or range. When the Worksheet_Change event-handler procedure is called, it receives a Range object as its argument. This Range object corresponds to the cell(s) that changed.

Assume that your worksheet has a range named InputRange, and you want your VBA code to monitor changes to this range only. No Change event exists for a Range object, but you can perform a quick check within the Worksheet_Change procedure. The following procedure demonstrates this:

Private Sub Worksheet_Change(ByVal Target As Range)
   Dim VRange As Range
   Set VRange = Me.Range("InputRange")
   If Union(Target, VRange).Address = VRange.Address Then
      Msgbox "The changed cell is in the input range."
   End if
End Sub 

This example creates a Range object variable named VRange, which represents the worksheet range that you want to monitor for changes. The procedure uses the VBA Union function to determine whether VRange contains the Target range (passed to the procedure in its argument). The Union function returns an object that consists of all the cells in both its arguments. If the range address is the same as the VRange address, VRange contains Target, and a message box appears. Otherwise, the procedure ends, and nothing happens.

The preceding procedure has a potential flaw: Target may consist of a single cell or a range. For example, if the user changes more than one cell at a time, Target becomes a multicell range. As it is, all of the changed cells must be within InputRange. If you still want to act on cells within InputRange, even if some of the changes are not, you have to change the procedure to loop through all of the cells in Target. The following procedure checks each changed cell and displays a message box if the cell is within the desired range:

Private Sub Worksheet_Change(ByVal Target As Range)
   Set VRange = Me.Range("InputRange")
   For Each cell In Target.Cells
     If Union(cell, VRange).Address = VRange.Address Then
        Msgbox "The changed cell is in the input range."
     End if
   Next cell
End Sub 

Using the SelectionChange event

The following procedure demonstrates a SelectionChange event. It executes whenever the user makes a new selection on the worksheet:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
     Me.Cells.Interior.ColorIndex = xlNone
     With Target
        .EntireRow.Interior.ColorIndex = 35
        .EntireColumn.Interior.ColorIndex = 35
     End With
End Sub 

This procedure shades the row and column of the selected cells, making it easy to identify. The first statement removes the background color of all cells. Next, the entire rows and columns of the selected cells are shaded light green. Figure 46.2 shows the shading.

Using the BeforeRightClick event

Normally, when the user right-clicks in a worksheet, a shortcut menu appears. If, for some reason, you want to prevent the shortcut menu from appearing, you can trap the RightClick event. The following procedure sets the Cancel argument to True, which cancels the RightClick event—and, thus, the shortcut menu. Instead, a message box appears:

Private Sub Worksheet_BeforeRightClick _
 (ByVal Target As Range, Cancel As Boolean)
    Cancel = True
    MsgBox "The shortcut menu is not available."
End Sub 

Using the OnTime event

The OnTime event occurs at a specified time. The following example demonstrates how to program Excel to beep and then display a message at 3 p.m.:

Sub SetAlarm()
  Application.OnTime TimeSerial(15,0,0), "DisplayAlarm"
End Sub

Sub DisplayAlarm()
  Beep
  MsgBox "Wake up. It's time for your afternoon break!"
End Sub 

In this example, the SetAlarm procedure uses the OnTime method of the Application object to set up the OnTime event. This method takes two arguments: the time (the TimeSerial function is an easy way to get a time, and the hour argument of 15 is 3 p.m.) and the procedure to execute when the time occurs (DisplayAlarm in the example). In the example, after SetAlarm executes, the DisplayAlarm procedure is called at 3 p.m., bringing up the message.

You could also use VBA's TimeValue function to represent the time. TimeValue converts a string that looks like a time into a value that Excel can handle. The following statement shows another way to program an event for 3 p.m.:

Application.OnTime TimeValue("3:00:00 pm"), "DisplayAlarm" 

If you want to schedule an event that's relative to the current time—for example, 20 minutes from now—you can write an instruction like either of these:

Application.OnTime Now + TimeSerial(0, 20, 0), "DisplayAlarm"

Application.OnTime Now + TimeValue("00:20:00"), "DisplayAlarm" 

You also can use the OnTime method to schedule a procedure on a particular day. Of course, you must keep your computer turned on, and Excel must be running.

To cancel an OnTime event, you must know the exact time the event was scheduled to run. Then you use the schedule argument of OnTime set to False. OnTime works to the nearest second. If you schedule something for 3 p.m., you can unschedule it with this code:

Application.OnTime TimeSerial(15, 0, 0), "DisplayAlarm", , False 

If you scheduled something relative to the current time and want to cancel it, you need to store that time. This code will schedule the event:

TimeToRun = Now + TimeSerial(0, 20, 0)
Application.OnTime TimeToRun, "DisplayAlarm" 

The TimeToRun variable can be used to unschedule it, assuming that the variable is still in scope:

Application.OnTime TimeToRun, "DisplayAlarm", , False 

Using the OnKey event

While you work, Excel constantly monitors what you type. As a result, you can set up a keystroke or a key combination that, when pressed, executes a particular procedure.

The following example uses the OnKey method to set up an OnKey event. This event essentially reassigns the PgDn and PgUp keys. After the Setup_OnKey procedure executes, pressing PgDn executes the PgDn_Sub procedure, and pressing PgUp executes the PgUp_Sub procedure. The effect is that pressing PgDn moves down one row, and pressing PgUp moves up one row:

Sub Setup_OnKey()
  Application.OnKey "{PgDn}", "PgDn_Sub"
  Application.OnKey "{PgUp}", "PgUp_Sub"
End Sub

Sub PgDn_Sub()
  On Error Resume Next
  ActiveCell.Offset(1, 0).Activate
End Sub

Sub PgUp_Sub()
  On Error Resume Next
  ActiveCell.Offset(-1, 0).Activate
End Sub 

By executing the following procedure, you cancel the OnKey events, and the keys return to their normal functions:

Sub Cancel_OnKey()
  Application.OnKey "{PgDn}"
  Application.OnKey "{PgUp}"
End Sub