Well, a way to do it in simple is an object that moves to the desired direction and then snaps back to its original position once its moved its own lenght. This can get tricky though. If you want it to move via a floating point, that is a value like 0.5, you'll need to store and set the objects position in a variable and then change that variable instead of moving it normally. Aside from the variable thing, this is basic fusion programming logic and it will do good on you to try to learn it yourself. If you get stuck, move on top something else and get back to it, see it as an exercise.