Are you referring to spoilerons where both ailerons go up to assist with harriers?

People started doing it to help with wing rock.. some planes are hard to harrier becauze you are fighting the wing rock constantly. I can't tell you how to program it because I don't use it, sorry.

Personally I don't see why people use it.. I think you should learn how to do it properly and most of the good pilots I have seen don't use it. Most of the common planes (Extra, Yak Edge, Sukhoi, Cap) will harrier properly once you learn how that plane likes to do it. For example, I can harrier most planes pretty well.. however last week I was flying a 40% Comp-Arf Extra for the first time and I couldn't get it harrier when my buddy can do it all day long. It just takes time to learn how the plane likes it. In the case of the Comp-ARF it's heavily throttle related.