>Is there an easy way to dynamically control the contents of a system menu popup? For example, is there the equivalent of a "BeforeDropDown" event that lets one control the contents of the popup just before it is displayed. I'm a little confused about how to use the ON PAD command as an opportunity to dynamically define or reconfigure the popup's bars and then (instantly) activate the popup as part of that menu pad. Thanks for your thoughts.

Menus are not OOP, so have no events. You can build the entire popup dynamically.
Just have the menu call a program that does this. You can also look at
GENMENUX to easily change menus on the fly.