Here is what orcad does: X_R1 N1 N3 N2 SCHEMATIC1_R1 .subckt SHCHEMATIC1_R1 1 2 t RT_R1 1 t {{@VALUE*(1-@SET}}+.001} RB_R1 t 2 {{@VALUE*@SET}+.001} .ends SCHEMATIC1_R1 @SET defaults to 0.50