It is a bit tricky but you can add a new rule and inside that rule set the named dimensions and parameters.
Inside a part add a rule. Here is an example, Blue words are parameters/dimensions from the part or sketch, so this block uses the two objects (DiamColl and DiamAtt) to change a diameter called Dcoll .
Dim RagColl as Double Dim RagAtt As Double RagColl = DiamColl/2.0 RagAtt = DiamAtt/2.0 If RagAtt < RagColl Then Dcoll = Sqrt((RagColl*RagColl) - (RagAtt*RagAtt)) Else Dcoll = 0.0 End If