Reversing CHOP data

Hello,
I was wondering if there is any way to reverse chop data? I am currently using a difference CHOP to measure change in movement between frames (with my webcam as input) and getting it to feed out the change in motion to a math CHOP. I want to use the values to drive the harmonic gain in noise TOP, but instead of having a higher value increase the harmonic gain, I would like to have the higher value lower the harmonic gain if that makes sense. In other words, a geometry constantly has noise, but as there is more movement detected, the noise decreases. Is there a way to do this?
Thanks!

I am no expert but I think changing signs in MATH chops for scaling and inverting or using MATH chops to scale stuff is worth experimenting with.