I have just been invited out  to the pub, so this is going to be very a very short short post.

Attached is the text of an example. xRotating box_2 will start to affect box_1 after the xRot exceeds 45°. When rotating box_2 you probably won't see any movement of box_1 until you release teh dial. Everything relevant is in box_1. The zTran in box_1 is slaved to the xRot in box_2. It is also slaved to a valueParm channel "HoldBack" in box_1. You can adjust the angle at which box_2 will start to move box_1 by changing the value of the "HoldBack" dial.

I will try to say more later,but perhaps not tonight.