[Lynne]

I still think a page is a better idea cuz if you do it in a thread, that means you are going to be doing some sort of condition to check the thread id every single time someone hits the showthread page.

But if you want to do it in a thread, I'd create a plugin at the hook location I suggested and first do a condition to check the thread id. If that passes, check the post id. If that passes, then do some conditions based on the usergroup and concatenate your stuff to the $post[messagetext] (or whatever it's called).