Custom registration form

[shrikie]

I need to make a custom registration form, adding normal fields isn't a problem, but I need to have a pulldown that has it's content (options) from a database.

Actually it's an organisation list, the user should be able to choose from which organisation they're from.

Can anyone give me some starting pointers how I best take on this problem?

Thanks

Actually, I need them to either : select and existing organisation they belong to, OR create a new organisation (Name + Addres).

How difficult will this be?