Create User Wizard

Can I change the create user wizard to add a field to populate the 'Comment' field in the aspnet_membership table? if so, how? 

also, how would I set the username (which is going to be an email address) to the email address field as well and also do a reg-ex validation on the username field to see if it matches the email format when the 'Create User' button is clicked, but before it is created.

Thanks
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