'richardson' got it :-) Multiple magnets created for the mattress... then parented to the body parts. That way the magnets stay attached to the body parts, but don't effect the body parts... only the mattress. Therefore... as the magnetized body part comes in range of the mattress it creates the indentation. I am currently magnetizing a figure from head to toe... with good results. The good thing is that when you save the figure... it also save the magnets with the figure. You can then reload the figure and use as normal. The magnets only come into operation when the mattress is also loaded into the scene.

"You don't have to be mad to use Poser... but it helps"