Biscuits and VWD, thanks! I didn't see any 'utility' to clear the exchange folder... where is it and what's it called? VWD, I was certain there already was a button in the collision object's panel that allowed you to clear previous, but I must have been imagining it. A check box as you describe would work well, I think. I tend to be a bit lazy with the interpolation/tweening, setting two frames and letting the animation run (I don't do animations, just poses), so tend to miss hands passing through legs, for example. Being able to just clear the exchange by checking a box would make tweaking the pose and re-running it a lot easier.