Multistep registration form depending on autoassigned role

Hi,

((ALL THIS IS FOR DRUPAL 6.6))

I'm currently creating my first Drupal website and my first problem comes up here.
For my registration process, I installed the Auto Assign Role module in order to allow user to select a role. So this works perfectly !

But i'll like to go a step further and have my user filling up a form depending on the role they just choose.

Concretely:
Multipage registration:
First page:
User choose enter their username, email, password and their role (normal or pro)

Second page:
If the user is a "normal user", a form asking for example his hobbies, his birthday ...
If the user is a "pro user", a form asking for example the address of his company, the name of the owner of the company (and to make it perfect a payment module, but this can wait)

I think you have pretty much the process in mind.

I looked over and over on the website and this is frequently asked but no concrete solution exist.

Does anyone has a clue ?

Thank you very much.