Need help in simulating differential Vias in HFSS

hi..am just beginning to learn HFSS.

I have to model differential vias and need to know at what separation the GND vias need to be added for the return path.

I have simulated the example project "differential vias" given in viawizard 3.1 folder.
But when i plot the E fields over the traces and vias. only one of the differential pairs is getting excited. But differential lines..both will be excited in the opposite directions right?

Am i missing something here. Please hep. Also i have attached an image of the sample model

You need to "turn on" the signalling that you would like to see in the field plots.

Go to HFSS -> Fields -> Edit Sources and modify

for differential, set both amplitudes to 1 and the phase to 0 and 180. This will give you your differential field plots

Thanks so much tallface65...
that solved my problem..thanks