title: Add UTM parameter based on events
body: <p>I know that it's best to add Google Analytics UTM parameters externally for incoming campaign traffic.</p>
  
  <p>However, when dealing with a juggernaut of an IT team who like to say "no" a lot I'd like to attempt to arm myself with a solid response. Analysts will feel my pain in trying to convince others to track campaigns the correctly, rather than by listening to a non analytics users advice of just creating segments based on URLs.</p>
  
  <p>There will be a campaign running where a visitor to the website will input a promo code in order to get a free thing.</p>
  
  <p>For whatever reason we cannot tag the incoming traffic or the links that will lead from the promo source with our UTM parameters.</p>
  
  <p>I can create an event in GA for when a visitor enters a promo code that relates to the campaign in question - the URL generated will contain the promo code int he URL, thus allowing me to create an event.</p>
  
  <p>Is it possible in Google-Analytics, combined with a lateral thinking developer, to overwrite the UTM parameters based upon a click event halfway through the visitor session? Could a script do this?</p>
  
  <p>Any other ways around it?</p>
  
  <p>We do have Google-Tag-Manager at our disposal too.</p>