How high can u go with this work? 

How high of a touch pad, do you mean? As high as your dog can easily place his forefeet up. Starting off, you don't want to go too high or you'll have a hard time teaching the behavior. But once the dog starts associating the cue with the behavior, you can apply this skill to almost any object.

Hope this helps.

Yes, exactly as Amy describes. I started with the kuranda bed, then I used square pads made out of foam material. (I have some pieces of them, which can be put and fixed one on the other), so I could gradually increase the height of the pad. Then up on to a banc , a chair, first steps of a (stable!) ladder, steps of a chairway etc. As Amy writes - wait until it works with a lower object so solidly that you can put the behavior on cue. Then you can increase the difficulty a bit and also generalize the behavior with very different objects.