how to do this?

[Hex_legend]

I have seen this done on a few vbulletin sites and I know it will take a lot of modding, but I would like some advice on how to do this.

I own a modelling agency and I'd like the registration page to show up with:

Models | Photographers | Hair Stylists

When they choose one of the options, each option takes them to a different registration page, with different questions. As its pointless having questions for a model for a hair stylist.

So the pages would be like:

modelregistration.php
photoregistration.php
hairregistration.php

All of which would register the user as normal, but put them into that particular usergroup