This has actually come up a few times before in the past few months. All such things (Domains, sub-domains, databases, E-mail, etc.) must be passed through the panel. You can set up a script to take the info submitted on your website, authenticate it self with the panel, and submit the information.
Keep in mind that you are responsible for all content store on your account, so if a user comes and puts up illegal sutff, or starts spamming, you’ll take all the heat and might well loose your account.
art.googlies.net - personal website