modeling two antennas in CST or HFSS

Hi
i am wondering is it possible in CST or HFSS to model 2 antennas with a certain distance between them and measure the S21 between them.
if anyone has successfully model such setup. i would appreciate if they uplaod their model.
any suggestions to create such model setup would be most welcome
regards

In Method of Moments codes without free space bounding and segmentation this is easy. Do you have antenna models to share for the test?