How do you reference a joint socket in an Animation Blueprint from a Level blueprint?

I have a skeletal mesh that has several bones. I want the skeletal mesh to be controlled by two objects. I first object Object A is parented to the mesh and moves just fine. However the second object, Object B needs to control one of the joints in the skeletal mesh.

However, when I am in my level blueprint I can not access the rotation of the joint in the animation blueprint.
how can i get a reference of the joint and set its rotation to match Object B?

This is for VR.
Thank you