From Vectorworks Developer
.VectorScript|VectorScript ..VS:Function Reference|Function Reference ..VS:Function_Reference_Appendix|Appendix
DescriptionProcedure ResetBBox forces the bounding box information for the specified object to be recomputed based on the objects' current geometry.
Call this procedure after modifying an object to force a redraw of the object.
def vs.ResetBBox(h): return None
h HANDLE Handle to object.
RemarksForces the bouding box information for object h to be recomputed based on current geometry.
This doesn't seem to work on symdefs.