I've figured it out. Look at the code that I've used on my forum for the "extra" button:
PHP Code:
<td width="73" height="31" id="extra"><a href="$show[nojs_link]#extra"><img src="$stylevar[imgdir_misc]/hdr_nav_extra.gif" width="73" height="31" border="0" alt="" /></a><script type="text/javascript"> vbmenu_register("extra" ,1); </script></td>
<div class="vbmenu_popup" id="extra_menu" style="display:none">
<table cellpadding="4" cellspacing="1" border="0">
<tr><td class="thead">Xbox Live</td></tr>
<tr><td class="vbmenu_option"><a href="leaderboard.php">Leaderboard</a></td></tr>
<tr><td class="vbmenu_option"><a href="forumdisplay.php?f=74">Clan Sub-Forum</a></td></tr>
<tr><td class="vbmenu_option"><a href="goto.php?section=clan">Aanmelden Clan</a></td></tr>
<tr><td class="thead">Overig</td></tr>
<tr><td class="vbmenu_option"><a href="goto.php?section=chat">IRC Chat</a></td></tr>
<tr><td class="vbmenu_option"><a href="goto.php?section=elite">Elite users</a></td></tr>
<tr><td class="vbmenu_option"><a href="/archive/index.php">PDA versie</a></td></tr>
</table>
</div>