My ragdoll...sort of

I am still doing this rope thingy... and I want to be able to move the bones of a mesh with the collision objetcs...

So I have a callback similar to the one in the ragdoll class..

And I have the position and orientation of each one of the boxes that the rope is made of...

So all I need is to take that GLOBAL position and orientation (which I presume is what the callback gets) from the collision box, and make the bone have the same one... the problem is bones use LOCAL positions...relative to the parent...

So how do I trasform my global position and orientacion into local position and orientaton....

I know is there in the code walaber did for ragdoll... but could someone explain it a bit better because I really don't know what he is doing..