Equation coefficients depending on parameters to estimate

I’m trying to estimate a model where some of the coefficients in the model equations depend on the estimated parameters. For instance,
where a and b are complicated functions of the parameters I want to estimate.
The coefficients are computed using a matlab function. I have tried to add the changing coefficients in the model section of the mod file using #, however, it does not recognize the matlab function and throws an error. Is there a way I can do this in Dynare?


Use external functions, available since Dynare 4.2: