Use CST MWS to calculate the interaction impedance of SWS

Hi all, did somebody use the CST MWS eigen mode to calculate the interaction impedance of slow wave structure. As we know, there is a SWS model (helix SWS) and also a template in CST example to calculate the interaction impedance. But that template seems only to calculate the impedance in the box center? I am not sure, if I want to calculate another position but not the center, How can I update the template code?
Thanks a lot.