small and easy order system?

[L1nux]

Hello,
I'new with ispCP and need some help.

I forgive free webspace and would like to provide customers a simple and immediate registration.
So far, I have to enter each customer and unlock manually.

I would like a simple PHP script which automatically gives the customer an account with ready resources (eg funpic, ohost or php-friends) and all with only three input fields:

-subdomain (customername.mydomain.com)
-e-mail
-PW

How do I put on the best and which files need to be adjusted?
Maybe someone is indeed of even kind enough to help me a little.

regards,
L1nux

(sorry for google translation)