Kangaroo Question

This may be a very simple question, but I am quite new to kangaroo so please give me some advice.

I was looking at this (https://vimeo.com/48658990) by Daniel Piker and find it very interesting so I am trying to work out a script for that and find some problems.

I want the unary force to only act once when I hit the toggle button without continually affecting the path of the ball. Is it possible to set up some sort of time frame restriction for the unary force or should I use some other force components for this?

Below are the files:

game.3dm

game.gh

Thanks.