Coupled electromagnetics-solid mechanics study

Hi,

I'd like to couple an electromagnetical eigenmode study to a forced-response solid mechanics study. More specifically, I want to do the following:

1. Solve electromagnetics model for two eigenmodes with slightly different frequency (frequency difference delta_f)
2. Add these two fields to obtain the total field
3. Calculate the optical forces generated by the total field (Maxwell stress tensor)
4. Use the optical forces as input for a frequency response solid mechanics study (as a function of delta_f)

Especially step 4 is troubling me: I have no clue how to connect the two studies. Does anyone have some tips?

Thanks!