>I would like to execute a program (*.prg) when the user exits a textbox via the return key but not trigger the program if he tabs or clicks out of the textbox. Any ideas on how to do this?

What about to put this in LostFocus Event of the TextBox:

IF LASTKEY() == 13 && ENTER
   DO WhatEver
ENDIF
DODEFAULT()

or in KeyPress Event of the TextBox:

IF nKeyCode == 13 && Enter
   DO WhatEver
   NODEFAULT          && I am not sure if these two lines at the bottom is neccessary
   KEYBOARD '{TAB}'
ENDIF