Combining magnitudes of different frequency in the emw model

Hey everybody.

I have been working in the RF>Electromagnetic waves (emw) module trying to reproduce the system described in the comsol notes: 'Optical Scattering Off of a Gold Nanosphere'

www.comsol.com/model/download/...tics.scattering_nanosphere.pdf

I can obtain all the variables that I am interested in (electric field, displacement vector...) for all the frequencies that I want just implementing a parametric sweep and the command emw. So for each single frequency I know the above mentioned E, D...

However, now I want to make some maths combining the electric field at different frequencies. For example, I want to know the sum of the electric field E1(w1) at a certain frequency w1 plus the electric field at another different frequency E2(w2) in one of the boundaries of the system.

Does anybody know how to do it?

Thanks.