To prevent the program from running multiple instances, just use the app.previnstance properties. This property returns true when there is another instance running. You can call this property in the LOAD event of the program to determine. If the return value is true, you can display a message to the user, further, before closing this new instance, you can activate existing instances, which is also a mode in which most programs are employed. The following code can display a warning message when necessary:
If app.previnstance the msgbox "Another Instance of this Program is already open." Appactivate app.title unload mendiff
