frequency-dependent material - with coupled physics

Hi,

In the RF module, I have two EMW physics (emw1, emw2) with user-defined frequencies, f1 and f2, which are fully coupled and solved simultaneously in the frequency domain. So for example, f1=1e14[Hz], f2=2e14[Hz], then emw1.freq=f1 and emw2.freq=f2.
I also define an analytic function for the relative permittivity dependent on frequency, epsr(fx), so epsr(emw1.freq) is not equal to epsr(emw2.freq).

I would like to define a new material, with the relative permittivity being "epsr(fx)". I would like fx, the input to epsr(), to be dependent on the current physics, i.e. the physics that's calling the material rather, as I have two.

One option for me would be to define the relative permittivity in the physics, overriding the material definition, by choosing Model->EMW1->Wave Equation->Electric Displacement Field->Relative permittivity and changing it from "From material" to "User defined", then defining it with my function, "epsr(f1)", and the same for EMW2 with "epsr(f2)". However, it seems intuitive that I should be able to go to the Model->Materials and in my material define the relative permittivity to be something like "epsr(activeemw.freq)" or in the essence of "epsr( if_being_called_from_emw1_then_emw1.f1, else if_being_called_from_emw2_then_emw2.f2 )".

Has anyone ever faced this problem?

Thanks