the above file is something i am working on. the boxes are controlled using PMO and i am having a problem with them when they collide with each other. so far i have got a "working" system but unfortunately the work around i have implemented means that they bounce on top of one another when they collide.
I had a similar issue to solve in True Diamond. You'll need two sensors, one to detect the top of a box and one to detect the bottom. That way the box isn't detecting the box, instead the bottom of the box is detecting the top of a different box.