<CST FD-Solver> Use experimental values of material pa

Is it possible to force the frequency domain of CST MWS to use the material parameters (permittivity/permeability versus frequency )defined in a file or a list? I know that it is possible to load material parameters (permittivity/permeability versus frequency) from a file and use several fitting schemes. But for the FD solver such a fitting scheme is absolutely unnecessary. And usually the supplied fitting schemes are not adequate.