Attached Link: http://www.afx.com/tutorial/iktut.htm

There's a great tutorial at the Autonomous Effects site (go to the link) on using Inverse Kinematics in RDS. I'm sure it would apply to Carrara. I bring this up, because they have you create a "target" object in the tutorial, which sounds like the THO's you're talking about. It's definitely worth checking out. - Dex