Jamie:
Easy!! Just add the following to the keypress() event.

do case
case tnKeyCode = -1 and tnShiftAltCtrl = 0 && F2 key brings up our Help
* We want the F2 key to drop the list down. F4 is the default key to do that.
nodefault
KEYBOARD '{F4}'
endcase

I've done quite a lot with changing the behavior of combo boxes. If you have other questions, just ask.