Hey K, sorry man but I cannot help you with this one
I suck with expressions, so Danny Might be the best person to ask regarding this
I DID have a brainstorm about a possible idea of assigning collision events to your objects, and just making the actual events NOT occur, (i.e. value/intensity/rate=0 or false), thus giving you the ability to just output the collision data. (?)
...not sure if that will work or not...but...
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS