Prevent duplicate entry into aspnet_profile table through CreateUserWizard?

Is it possible to setup the CreateUserWizard to check for a duplicate entry in the aspnet_profile table (for a custom field) before the new user is created?  For example, if I added a phone number field and wanted to make sure nobody else could create an account using that same phone number if a user already has an account with that phone number in the aspnet_Profile table's PropertyValuesString row? 


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