One solution is to use wildcard domains (Your host will have to set it up, and you will need a dedicated IP address). With wildcard domains, XXXX.yourdomain.com will go to your website regardless of what is entered for XXXX. You can then use .htaccess or php scripting (or more likely both) to handle the XXXX how ever you want. I've used this solution several times. -JasonR
Simple, code a cUrl script that will log into your cpanel each time and add that subdomain. I advise learning cUrl first and then just post the information a page at a time.
cUrl is Good idea but what if some subdomain available to register? Look at this Article : http://photomatt.net/2003/10/10/wildcard-dns-and-sub-domains/
Wildcard domains is the safest option, but wildcard domains are NOT supported by default if your server is powered by cPanel. That's a serious disadvantage of cPanel. Wildcard domains allows you to easy manage sub domains, delete them, add them ... all easy, quickly (with a mysql db) and efficiently. Using cURL is an option too, however it requires a whole lot more programming, and also its more difficult to manage. And, maybe your subdomain count is limited in cPanel? If you can go for wildcard domains, stick with that!