CDJ 2000 Nexus Loop Cutter

I'm using scratch live on Pioneer 2000 & Pioneer 2000 Nexus. The regular 2000 had a really cool feature called 4 beat/ loop cutter. When this is pressed it puts the track in a 4 beat auto loop. When the same button is pressed again it will cut it in 1/2 and so on. The Nexus seems to not have this feature but its just a MIDI signal. How can I assign a button on the Nexus to do the same effect! PLEASE HELP ASAP