Hi,
last year I had to search the web quite a lot on this subject. I needed to analyze an analog signal coming from a couple of hall effect sensors. I used an arduino for the A/D convertion of both sensors. As I don´t have Matlab's "serial communication" toolbox (don't know If it's called like that, but I guess it is..) I decided to try with scilab (an open source Matlab-like application). There is a scilab function here that may help you:
http://www.gds-sw.de/goodies.htm
it's called serial.dll, just select your COM port, bit rate, byte length, parity, etc, and you will be able to reciebe the data. scilab uses almost the same commands as Matlab.
I know it's not exactly wat you wanted, but give it a try if you have no other options
good luck