DoEvents Function

Note   The function, method, object, or property described in this topic is disabled if the Microsoft Jet Expression Service is running in sandbox mode, which prevents the evaluation of potentially unsafe expressions. For more information on sandbox mode, search for "sandbox mode" in Help.

Yields execution so that the operating system can process other events.


DoEvents ( )


The DoEvents function returns an Integer representing the number of open forms in stand-alone versions of Microsoft Visual Basic, such as Visual Basic, Professional Edition. DoEvents returns zero in all other applications.

DoEvents passes control to the operating system. Control is returned after the operating system has finished processing the events in its queue and all keys in the SendKeys queue have been sent.

DoEvents is most useful for simple things like allowing a user to cancel a process after it has started, for example a search for a file. For long-running processes, yielding to the processor is better accomplished by using a Timer or delegating the task to an ActiveX EXE component. In the latter case, the task can continue completely independent of your application, and the operating system takes care of multitasking and time slicing.

Any time you temporarily yield to the processor within an event procedure, make sure the procedure is not executed again from a different part of your code before the first call returns; this could cause unpredictable results. In addition, do not use DoEvents if other applications could possibly interact with your procedure in unforeseen ways during the time you have yielded control.


Note   Examples that follow demonstrate the use of this function in a Visual Basic for Applications (VBA) module. For more information about working with VBA, select Developer Reference in the drop-down list next to Search and enter one or more terms in the search box.

This example uses the DoEvents function to cause execution to yield to the operating system once every 1000 iterations of the loop. DoEvents returns the number of open Visual Basic forms, but only when the host application is Visual Basic.

' Create a variable to hold number of 
' Visual Basic forms loaded and visible.
Dim I, OpenForms
For I = 1 To 150000 ' Start loop.
If I Mod 1000 = 0 Then ' If loop has repeated
' 1000 times.
OpenForms = DoEvents ' Yield to operating system.
End If
Next I ' Increment loop counter.

Applies To: Access 2007, Access 2010 Developer, Access 2013 Developer, Access 2007 Developer, Access 2013, Access 2016, Access 2010

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