hfss bandwidth

This has been puzzled me for a while. There's no such thing like a "3dB BW" in HFSS. I understand you may watch the s11 curve and measure the portion higher than -10 dB for the bandwidth. But how can you optimize it? Is there a way to write an express in "output variable" to calculate the 3dB BW automatically?

Thanks

Added after 2 minutes:

I did come up an expression like "if(max(dB(Gain))-dB(Gain)>3, db(Gain), 0)", which draws two sharp ramps on the 2 edges of the 3Db BW for visual recognition. However, it can't calculate the bandwidth.

humm, tough question?