how to simulate microwave cavity in CST software?

i'm having problems on how to simulate or run my microwave cavity design in CST software..if anyone knw a way to get the radiation(EM waves) pattern inside my microwave cavity..please lend me a hand here..in fact..any suggested software is good too..the thing is..i wanted to check whether my microwave design has somewhat a leakage radiation or not...thats the problem..so..if i can simulate my design..and analyze the results..and if theres no leakage..i can proceed on doing the hardware..please..

any ideas will do...hee