Link in postbit to user's first post / thread in specific forum
 

I'm trying to figure out how to write the code that I can use in the post bit as a HREF for finding the user's first thread / post in a specific forum.

In my forum, all users have to make an introductory thread before they can post on the rest of the site. I want to have a link in the postbit that will point back to that thread. I'm unsure what is necessary to do that though.

For reference, they can only create one thread in the intro forum, and it will always be their first thread / post on the site.. Any insight or know of a mod that already has this functionality? TIA!