question on modelling a varactor in CST - Tunable Patch

Hi,
I have designed an SIW cavity backed rectangular patch and would like to change its resonance frequency by using a varactor. The simulation package I'm using is CST MWS. What I have done is I've inserted an inductive post (a conductive via) somewhere near one radiating edge of the patch, and then added a lumped capacitor in series with one edge and the post. To see the effect of the varactor, I just change the capacitance value of the element. Does this seem right to you? If not, could you please advise me on the matter?