Hi Johan,

To accomplish this, you'll likely need to subclass one of the membership providers and override one or more of the methods in this class.  In your description, it sounds like you might want to subclass DotNetNuke.Security.Membership.AspNetMembershipProvider and override the CreateUser method.

Compile this as a separate assembly, and update your web.config to use your custom provider (instead of the default one).  I would rank this as a moderately difficult development task.

Good luck!

Brandon