Motion tracking help

I am completely new to MAX and i am trying to complete a final project for class. What i am simply trying to do is have the program adjust volume/pitch/velocity depending on where i place my hands on the screen.
Right now, I have a video matrix that splits my video into a 4X4 matrix. I used the left most column to detect the grey values presented and as they change, i initiate a slider change. So when my hand is in the bottom left box, slider moves to 10, i move up a box, slider moves to 20 and so on. The problem i am having is that the grey scale values are NOT consistent. I have to adjust each value whenever i change rooms i am in.

My question is, is there an easier approach at doing this? preferably tracking a specific color, and depdending on where it is positioned on screen will trigger the slider to move up or down. I provided a screen shot of what i have so far.. I also have seem many videos on youtube with individuals doing something very similar to me. Clicking buttons and adjusting things just by moving their hand to a specific object.

All help is greatly appreciated!