WD97: Shell Command Does Not Wait for Application to Finish

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Visual Basic for Applications processes macro commands asynchronously. This means that each command runs independently of any timing process, such as a clock.

Because macros do not wait for the launched program to finish before running the next command, this can cause problems, particularly if subsequent commands rely on results from the launched program.

Microsoft provides examples of Visual Basic for Applications procedures for illustration only, without warranty either expressed or implied, including, but not limited to the implied warranties of merchantability and/or fitness for a particular purpose. The Visual Basic procedures in this article are provided 'as is' and Microsoft does not guarantee that they can be used in all situations. While Microsoft support professionals can help explain the functionality of a particular macro, they will not modify these examples to provide added functionality, nor will they help you construct macros to meet your specific needs. If you have limited programming experience, you may want to consult one of the Microsoft Solution Providers. Solution Providers offer a wide range of fee-based services, including creating custom macros. For more information about Microsoft Solution Providers, call Microsoft Customer Information Service at (800) 426-9400.

This Visual Basic for Applications macro sample uses a combination of a Do Loop with the Exists method to determine if the launched program is still running.

      Sub IsTaskRunning()
      ' If file does not exist, GoTo error trap.
      On Error GoTo itrErrTrap
      ' Run sample batch file in MS-DOS window.
      Shell "c:\test.bat"
      Do
         ' Note: When specifying the Application name
         ' with the Exists(Name) argument, omit the
         ' Application extension.
         test = Tasks.Exists("test")
      Loop Until  test = 0
      MsgBox "The application has quit."
   itrErrTrap: ' Note: This line must be left aligned.
      If Err > 0 then MsgBox Err.Description
   End Sub