How can we use an FTDI chip in matlab or simulink?

Hi all, I have an FTDI FT232RL chip that acts as my Virtual Comm port. I have connected an XBee module on its output to sransmit my data wirelessly. Now the problem is: as I open tmtool (Test and Measurement Tool) in Matlab, it shows me that there is something present in Serial port form but when I click 'connect', it gives me an error. Can anybody tell me how can I remove this error? I am basically an amateur in matlab and simulink, I found an S-function too but I dont know how to use it. I am attaching a screenshot of the thing. <http://oi40.tinypic.com/6qcgup.jpg>

[Usman]

the same ftdi thing works great in XBee's software X-CTU. I have used it to test and run my wireless things.