External Axis

I want to create external axis in my robot studio simulation.

I have one rotary mechanism.

I want to make that mechanism as my external axis.

Is this possible?

I do not want to do with mechanism pose options.
I want to make that mechanism as my external axis so that i can give parameters  in my      Robot targets-external axis.

Please help me how to do this.

I believe this can be done in RS.

I am awaiting........................................