Maybe you wan't to do the transition from real to fixed point in matlab.
There should be something (in the fixed point toolbox) named "fixed point objects"
Doing that you'll can do the validation of certain fixed point resolutions in matlab.
After you've implemented the above in HDL an
ecquivalency check against your matlab
results is sufficient for verification, which is a
huge advantage, because you can have
your computer do it for you.
Since VHDL2008 there should be fixed point and floating point type packages.
The libraries are free for download (google should do the trick).
I've no experience with that libraries except that I've successfully compiled an example
with QII a long time ago.