Reply to Pro Scratch- For Digital DJs - Like Ean

So we all know that digital DJs, or controllerists, like Ean Golden can't really scratch like DJ Craze or DJ Shiftee. They move the crossfader and everything to get a perfect scratch sound. To me- it sounds like a lot of work. So I thought of another way to do.

I want to be able to press a button on any controller- in this case I have a mini midi fighter i made from a numpad- and this would be for scratch performances only. When you are holding the button down- the volume is at maximum for that deck your scratching on. However, once you let go- the volum stops. So it sounds almost exactly like the scratching crossfader technique. There is a video I found a few days later after i got the idea of a guy who actually did it,

http://www.youtube.com/watch?v=lqTIDYCmXq8

So the big question is:
HOW DO I MAP ITT