EmailAddress should not change even if Firstname and LastName are changed

Hi,

My issue is when user changes his firstname and lastname, defaultemailaddress is getting changed. I removed overwrite checkbox and added 

If Not $[Isloaded]:Bool$ Then

'my code to generate emailaddress

End If

as suggested in below link

https://www.quest.com/community/one-identity/identity-manager/f/identity-manager-forum/6103/centralaccount-name-should-not-change-after-update-the-firstname-ad-lastname-of-users

still the email address is getting changed. Please suggest.