[Gio~Logist]

Actually, if you are tyring to make this go in a post, then this would not work:

<if condition="$post['fieldx'] AND $thread['forumid'] == y AND !is_member_of($bbuserinfo, z)">
      $post[fieldx]
</if>

You'd have to use this:

<if condition="$post['fieldx'] AND $thread['forumid'] == y AND is_member_of($post, z)">
      $post[fieldx]
</if>

$bbuserinfo is the userinfo of the user that's browsing the forum. $post is what draws the userinfo of the poster.