In hook: forumbit_display
Put the following code, and play a bit with togling the collapse values.
PHP Code:
global $depth, $tempext, $collapseobj_forumid , $collapseimg_forumid, $show;
if ($depth == 1 AND $tempext == '_nopost')
{
global $vbcollapse;
$collapseobj_forumid =& $vbcollapse["collapseobj_forumbit_$forumid"];
$collapseimg_forumid =& $vbcollapse["collapseimg_forumbit_$forumid"];
$show['collapsebutton'] = true;
}