Great, so if you've worked at that level of coding before, we just need to know where it is you're having trouble.
Here's a number of articles
here on CP[
^] based on a serial port modem search.
And here's a way to test for caller id support on your modem, along with the sample result string:
https://secure.mtnsys.com/Pages/howto/htmdmtst.htm[
^].
It says that "AT#CID=1 or AT+VCID=1" are the strings that most modems use to activate call id on the unit itself. You'll need to check your modem documentation if that's not correct in your case.
Cheers.