Question: Switching between Active and Passive Joints in MapleSim

Does anyone know how to switch a joint between having a prescribed motion driver and acting as a passive joint? More specifically, I am building a bed of spring to serve as a model for haptic feedback on a Phantom Omni device. Therefore, I need to read the position of the device (which is not a problem) and then based on the position of the device calculate a force to feed back to the device.

Consider the simplified example below. In one situation I may need to give a position input to the spring on the left and obtain the force output, while the prismatic joint on the right is a passive joint. In another situation I may need to give the prismatic joint on the right a position input and obtain the force output, while the prismatic joint on the left is a passive joint.

If I do not give an input to one of the sides, the simulation does not work properly. Any thoughts?

Spring_Model_with_Mu.msim