Updating CO when user clicks button in email

Here is my use-case:

We have an email (Registration Confirmation) inside Eloqua that is automatically triggered through ATG when a user creates an account on our eCommerce platform.  The email is sent to verify the user's email address and to confirm registration.  This email is NOT a part of any pre-set campaigns, it is simply fired off each time a user creates an account. 

What I would like to do is once this email is sent, I wan that user added to a pre-built, ongoing Nurture Campaign.  Once in the campaign, I want to determine if the user clicks on the button inside the email (meaning they've verified their email address), have that click update a value in the associated custom object record so that they can begin to receive a pre-set cadence of emails.  If after a few days their custom object hasn't been updated, I would like to send a second account verification notice email as a reminder that they need to