Question about remote account creation

I am working on a website where people will be able to sign up for hosting accounts though a form and it will create the account automatically. I have the code from Accounting.php.inc so I know I can create an actual account, but I'm wondering is there a way to create a subdomain for that account and allow ftp and cpanel access to that account. So for example we have a package set up for 200 megs of disk space, so much bandwidth, etc. and when they fill out the form it creates http://[b]username[/b].domainname.ext/ and they can ftp and access cpanel through that.

So my question is, is this possible? If so, is there a file similar to Accounting.php.inc that can be used?

Any help would be great.

Thanks!