Search in current forum only

[ehmud]

I have added search form in forumdisplay.php above the thread to search required threads. I am using this code, what to change this code because I want it to display search results only from current forum, not from all forum.

<form action="search.php?$session[sessionurl]do=get&forumid=$foruminfo[forumid]" method="get" name="vbform" id="searchform">

I have also attached snapshot here with;