Rotate root prim around child prim

[Ruthven Ravenhurst]

Hi, I'm using U-Poser to create an animation. Since animations use the hip as the root, I'm trying to figure out how to simulate using the head as a root. I have rezzed a prim, and made it the same size//shape/rot/pos as the head on the model. I want to set a timer to check the orientate of the head on the model, and tell me how I should move/rotate the root so that the model head matches the reference prim. 

I hope that makes sense. I think it's probably a math formula, but I'm not great at 3D math, so I'm not sure which order to calculate the different values to get the result I need.

The problem is, the root of the model is actually the platform on which it is standing. The hip joint is what rotates the avatar, and the Root (not the object root, but avatar Root) is what sets the position

[Ruthven Ravenhurst]

I basically just want the reference prim to spit out a position and rotation offset, which I can then copy and paste to the appropriate settings on the u-poser hud

[Ruthven Ravenhurst]

And of course, after rotating the model to the right orientation, the offset to the head will be different