User Creation Rule

Summary

User Creation rule

Content

There is a user creation rule setup as below when new employee is created 

* If Work Email exists then user name will be Email

* If No Work Email, then user name will be first_name.last_name

Now when an employee is created without email, the system generated a user account with first_name.last_name. say after a week when we add an work email , is there any setup or process which can update the user name with email address automatically ?

Thanks

Jag