Limitations of Embedded MATLAB functions: Filter design in EMF possible?

Please note that I am using Matlab 2009b for my project. Nonetheless, I am convinced that this does affect later versions as well.

I have the following simple setup that does not work:

• My MATLAB script to execute the simulation:

clc
sim('main');

• The Simulink Model with the EMF:

The content of the embedded MATLAB function:

function output  = PSF_SW(freq_peak)

order = 30;
freq = [0 freq_peak-0.2 freq_peak-0.1 freq_peak+0.1 freq_peak+0.2 1];
mag = [0 0 1 1 0 0];

output = firpm(order,freq,mag);

Executing the MATLAB script, I receive the error message:

??? Error using ==> runmain at 4
Error due to multiple causes.

Caused by:
    Error using ==> runmain at 4
    Error reported by S-function 'sf_sfun' in
    'main/Embedded MATLAB Function/ SFunction ':
    Errors occurred during parsing of Embedded MATLAB
    function 'Embedded MATLAB
    Function'(#18)
    Error using ==> runmain at 4
    Error in port widths or dimensions.  Output port 1 of
    'main/Embedded MATLAB Function/freq_peak' is a one
    dimensional vector with 1 elements

As you can see, I want to design a digital bandpass filter in real-time. However, this seems to be impossible since the error occurs each time the inputs of firpm depend on the inputs of the EMF. I do not receive an error, if I define freq_peak inside the EMF. Is there another way to do this? Is this problem related to the fact that MATLAB's code generation procedure does not allow dynamic memory allocation?