>So, have you used this reliably? Obviously I can write my validation code to process the MDOWN() function, but are there some conditions, such as a slow or overloaded PC or super fast mouse where it will not work?

Nope, thats where the Boos and Hisses might come in. Also, I can't test it right now, but try the MouseDown event fpr each of these buttons and tell me if that works, I never remember trtying that one.