>How do you open a combobox programmatically when user types {Enter} while in it?

By default, Enter moves focus to the next control in the tab order. I'm not sure it's a good idea to change that. Anyway, you can get desired result with following code.

* Combobox Keypress
LPARAMETERS nKeyCode, nShiftAltCtrl
IF nKeyCode = 13
	KEYBOARD "{ALT+DNARROW}" CLEAR PLAIN
	NODEFAULT 
ENDIF