Changing the trigger to 'Any form post' worked. I've now modified the page to include server validation to check that the email address hasn't already been registered in the database before inserting the record. This seems to only work once the form has been submitted once - by that I mean opening the browser fresh (without a session variable being set) allows me to enter an email address that I know is already in the database and the form submits. If I then go back to the index.php and try and enter that same email address the validation works, but once I close the browser I can enter the email address again resulting in duplicate entries. I've attached the new index.php page and left you a link to the site in the private message
