>I am creating a custom button bar that automatically positions itself when the executable is launched. I have it setup to position itself at the bottom of the main FoxPro window. The problem I have is how to get it to reposition itself automatically after the user changes the size of the FoxPro main window.

this is easiest if you use a Top-Level form instead of _SCREEN, so you can just put code in the form's resize event. If you have to use _SCREEN, you'll need to instanciate a timer that checks the size and windowstate of _SCREEN at a given interval, and moves the bar as needed, when the size has changed.