[Closed] envelope question

i am writing a little script to adjust a number of envelopes on a mesh and move the end point to the pivot point of another bone. i have worked out the position is based on the pivot of thew bone being 0,0,0.

I am able to get the pivot point of both bones and iwork out the distance between the 2 bones
but when i apply this offset to the envelope it is the right length but at 90 degrees to the bone.

Is there a way of specifiying the pivot point of a bone to move an envelope end point to?