Skull, AFAIK you cant map two functions to the same button in AH.
But you have 4 modes (=stick sets) available. Mode 1 is for planes, Mode 2 is for vehicles/boats. I think Mode 3 and 4 are free for use. Map flaps down to the button in Mode1, then map Flaps up to the same button in Mode3. Now all you need is a button/key to switch between modes in flight.