I tried to get it for you, but HFSS seems to compute tangents in some strange way that involves lines and not surfaces. I know that HxH* is ComplexMag(CVec_H) (squared), and integrating over a surface you just have a ComplexMag(CVec_H) (squared), select geometry, select your surface, then press the integrate button.
Some more research is required....I'll let you know if/when I get it.