George,

Turn on event logging and checkout what's going on.

It appears that the mousedrag operation that you are performing is triggering the ProgramaticChange event to fire even though the When() should have prevented anything from happening. The GotFocus() never fires so the cbo doesn't get focus, but the mouse*, click() and progchange events still fire. I think you could put conditional code into ProgramaticChange() and NODEFAULT under the same condition that causes the When to return .f. ala:

if ( ! thisform.editing )
   nodefault
endif

>I would expect that the value of Combo1 cannot change, since the When( ) method returns false. This is not the case. The user can click on the center of Combo1, then drag out of Combo1 (either up or down). This changes the value, a little. Usually only a few values up or down.
>
>This is very scary behavior, as we have hundreds of forms with comboboxes on them, and the default behavior of the framework we are using is to have:
>

>RETURN thisform.editing
>

>in the When clause of all objects, and to only allow editing at certain times.