Hi,
For getting the coordinate values with hand as a origin,Do subtract your current x,y,z from your hand x,y,z values.
ex:
getting head coordinate values as hand as a origin:
head.x=head.x-hand.x;
head.y=head.y-hand.y;
head.z=head.z-hand.z;
hope this solve your problem.
Thanks,
Gowri