Script for a Back Button

If you want to code a script for a back button in your flow, you certainly can. This is not something we can code for you, but the below instructions should help you get set up:

Say your original campaign is this:
http://yourdomain.com/path/lp.php?trvid=10001&trvx=b0a82dd9&extid={clickid}&campid={campaign}&creaid={adid}

Then, you need to create an alternative campaign just for back button traffic using the same traffic source. Example:
http://yourdomain.com/path/lp.php?trvid=10002&trvx=c9k2d7x8&extid={clickid}&campid={campaign}&creaid={adid}

You will then want to include all the variables passed in from the first campaign when redirecting to the second campaign.

For example, visitor goes to campaign: 
http://yourdomain.com/path/lp.php?trvid=10001&trvx=b0a82dd9&extid=12345&campid=1001&creaid=abcd

They get redirected to your landing page:
http://lander1.com/?extid=12345&campid=1001&creaid=abcd

When they click back, you need to pass the entire query string into the 2nd back button campaign.

So this part:
extid=12345&campid=1001&creaid=abcd

needs to replace the query string part of the 2nd campaign, so you're putting the visitor through this 2nd campaign URL format:

http://yourdomain.com/path/lp.php?trvid=10002&trvx=c9k2d7x8&extid=12345&campid=1001&creaid=abcd

Then, the visitor will be redirected to:
http://lander2.com/?extid=12345&campid=1001&creaid=abcd