I have an assembly with a member that rotates on a shaft and has a torsion spring to keep it biased in one direction.  I would like to have one end of the torsion spring move with the part that rotates.  It would be ideal to have it do it dynamically but it's not required, it could move when rebuilt.  I have been able to make an end that moves with the part but the ending point of the helix doesn't change so the spring just bends at that point.  

Here it is in the "normal" state

And here it is with the part moved up.  You can see that the helix ending point remains the same while the extension moves resulting in a sharp bend.

Any ideas on how to get that helix ending point to change with the moving part or a different approach would be appreciated.

I'm using 2011 SP3. 

Thanks