View First Unread post

Hello,

i´m new to php-fusion, but already have a working site, with forum and several infusions.
I´m already using an infusion for the latest forum threads, but thats noch exactly what i´m looking for.
If i browse through the forum and enter threads i´m looking for a button "View First Unread post" something like that to go to the latest unread post.
Is it possible to edit this in the viewforum.php or anywhere else? Or is there an infusion for that?
Already found the thread where " MAX(p.post_id) as last_post, " is noticed, but this doesn´t work for me.
I´m using v6.01.15.

Help would be nice.

thx in advance