Hi ! I'm still using a 6527 device and I KNOW there's a great documentation about the DIG_Change_Message_Config function for VB... But there's no example using this function... And the docs doesn't explain the use of the callbackAddr for VB functions...
Have you looked at the attached zip file to that link I send you as well? Because the example there should demonstrate in VB how to perform change detection using windows messaging.