Thanks for the response, sorry I didn’t see it until now. I am trying to work with this again.
I’m still not having any luck even using https://www.example.com/code.php as the target URL.
Here’s my page: https://bit.ly/2M3O8sI
This results from the custom field approach where CODE1 is the field name, https://www.example.com/code.php is the field value and {{CODE1}} is entered in the page.