Words "MATLAB" and "Simulink" scare me. See, back at Uni they've managed to convince me that I in fact do not like math. Or know it, for that matter
I have just enough knowledge to understand what "zi = exp(-1.0j*pi*w)" does in kingshriek's script and why, or how to build my own function to compute frequency cutoff for a given FIR/IIR filter. But that's it. There is always a chance I will figure this out, probably by sheer luck trying every possible filter equation I can come up with, but that will take massive amounts of time and work.
I'm hoping someone with more experience in that matter could, with little effort, just pull something nice out of his/her magic hat