>But do that only if the .displayvalue is empty; if it's not, maybe some location related to the value would be better ("equal to" is also a relation :). I think it's possible for a user who drops the combo and has the mouse in the dropdown area to inadvertently select a value they didn't want - and your forcing of the selection to top may lead to a similar effect. YMMV.

That's true, but if the bound data field is empty then DisplayValue is also empty by definition.

The actual code in the combo DropDown event is this, so it only works if there is no value present. It leaves everything alone if the field has a value:

IF NOT EMPTY(this.ControlSource)
	IF EMPTY(EVALUATE(this.ControlSource))
		KEYBOARD "{Home}" PLAIN CLEAR 
	ENDIF
ENDIF

DODEFAULT()