Want to solve AIR BOX and virtual BOX for this Design HFSS - UWB

I have a problem in solving the air box virtual box of my design I need a help from professionals , I should be really thankful to you ..
A student from developing nation :(

Attachments_20131215.zip

You should first select the faces of the virtual box and choose Modeler>List>Face List in order to create a face list that can be chosen in the Radiation Surface tab when setting a radiation sphere.