You should try using the COMM api to access serial ports.
If you are running other than W2K you should be able to 'map' an IR port to a virtual COM port.
Then, just talk to your COM port through the COMM API.
If you are under W2K, you will need a Virtual COM mapper. (there's on made by a German company that is called IRcomm - not free but cheap)
I tried it with a mobile phone under W2K and it works.
But that doesn't mean you solve the problem of the protocol of your device...
Chris.