[Xenon]

first:
yes is allowed

second:
in newreply for example find this:

PHP Code:

$DB_site->query("UPDATE user SET
          ".iif ($foruminfo[countposts],"posts=posts+1,","")."
          $dotitle"."lastpost='".time()."' WHERE userid='$bbuserinfo[userid]'"); 


and change it to:

PHP Code:

$DB_site->query("UPDATE user SET
          ".iif ($foruminfo[countposts],"posts=posts+1,".iif($bbuserinfo[usergroupid]==2 and $bbuserinfo[posts]+1>=x,"usergroupid=y,",""),"")."
          $dotitle"."lastpost='".time()."' WHERE userid='$bbuserinfo[userid]'"); 


the changes in newthread would be similar