is it even possible?
You can create a "smart" part that is driven by a plane, where the plan is animated. That is how springs are animated in solidworks, the # of coils are held constant, but the plane that drives the length of spring is varied. This causes the model to continuously update its self. What type of assembly are you looking to animate?
edit: Here is a link with an example. Animate springs in SolidWorks - YouTube
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