calculating energy stored + hfss

Dear all,
When using eigenmode solver to simulate a resonator, I can get
a field distribution. I want to know, what is the energy storage of the
resonator regarding the simulated field distribution.
I want to know how much is the E field distributed when energy storage is given.

amicloud

use the fields calculator to calculate the integral of 1/2 E x conj(E) and 1/2 H x conj (H) over the volume to find the energy storage

Theory is easy,but When doing the integration it will be troublesome.And for different cases, there will need different calculation.
I think when simulating, Ansoft will give a standard and regulate how much the
energy will be given, with this,the field is simulated. I wnat to know the regulation of Ansoft.
Thanks

amicloud