use result from a study to calculate a variable and use this as input for another physics module

Dear COMSOL users,

I'm a student and attempting a RF system in combination with a DC magnetic field.

First, I simulated the magnetic field of my model in COMSOL. Now in my next study (frequency domain, RF physics) I need to use the previously calculated magnetic field to calculate the permittivity matrix: I need to calculate the local cyclotronfrequency, which depends on the local magnetic field (mfnc.Bz).

Now my question is: How do I use my result from the local magnetic field study to calculate all local cyclotron frequency and use this as input for my permittivity matrix in the RF module?

Thanks in advance.

Kind regards, Rik