Activating Another Application

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You might be wondering what steps to take if the application you want to use is already open. Using the Shell function would create a second instance of the program taking up valuable memory. In most cases, you should activate the program that's running, rather than creating a new instance of the program.

Consider the following example, in which the ActivateCalculator procedure uses the AppActivate statement to activate the application if the application is already running. The argument for the AppActivate statement is the caption of the application's title bar. If the AppActivate statement generates an error, it means the Calculator isn't running, so the procedure will start the application.

Sub ActivateCalculator()
    AppFile = "Calc.exe"
    On Error Resume Next
    AppActivate "Calculator"
    If Err <> 0 Then
        CalcTaskID = Shell(AppFile, vbNormalFocus)
        If Err = 0 Then MsgBox "Unable to start the Calculator"
    End If
End Sub

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