Using Sketch for top down design with mechanical mates/relations

I am trying to design a door hinge.  I created a sketch in an assembly that defines the motion of the door through simple lines/pivots.  I can move the components through their motion when in the sketch editor.  However, the relations freeze when the sketch is exited (sketch is under-defined on purpose so door moves).

I was then planning on creating the parts (door, frame, hinges) that would be constrained to the sketch.  Is there a way to keep the sketch from freezing when working at the assembly level?

Thanks,

Marty