How do I make my physics ball not jump on walls?

I just have a ball that jumps. When it hits a wall it jumps again, which I don't want. How do I make it so that when the ball hits the same object from the top side only and not the wall sides, it jumps?

The code is to jump when there is that object ground/wall, so this way there isn't infinite jumping.

a quick hack:

you could create an visbilbe objekt "wall" and a very thin and invisible object "floor". You would have to put the thin object "floor" ontop of your walls. Than in events you define, that when

- the ball hits the "floor" it jumps

- the ball hits just the the wall nothing happens.