I'm relatively new to DNN and am trying to modify the registration page so that there is a "Confirm email" textbox that will give an error if the user types in two different email addresses.  I found out where to add the textbox, but I was wondering if anybody could tell me where I might go to put in the logic that will check the two addresses and give an error.  Also, I'm using version 4.3 if that makes any difference.