Dynamic Blocks - Constraining movements

Can anybody explaind How can I constrain two circle's center points and have them move along the same arc with a rotation parameter?

I am trying to create a dynamic block of a robot for planning and want the arm and end efector to rotate independantly but have the end efector "follow" the arm rotation.

Block is attached if anybody wants to try.  

I already have the two separate rotation parameters defined.

Thanks,

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