Apply rotation from translation control rig

Hey guys,

I have a question concerning the control rig. I have set up a control rig for my humanoid mesh based on the UE skeletal mesh. It’s working fine but I wanted to improve it on the arm movement. Basically I want the top part of the spine to rotate when the arm is fully stretched so that the mannequin can reach a bit further. It means that a translation of the hand (which with my current control rig, control arm) should induce a rotation of the top spine if it’s needed. Any ideas on how to achieve this ?

Thanks