Hi there.
I'm wondering: how do I add an extra css class to all top level parents (meaning mainmenu items) using wp_list_pages function in wordpress 2.8?

See an HTML output example below (I want to add the bold code):
<li class="mainitem page-item page-item-30">
<a href="javascript:void(0);" title="Pages">Pages</a>
<ul>
<li class="page-item page-item-40"><a href="link-to-submenu-item1" title="link-title1">Link-desription1</a></li>
<li class="page-item page-item-41"><a href="link-to-submenu-item2" title="link-title2">Link-desription2</a></li>
<li class="page-item page-item-42"><a href="link-to-submenu-item3" title="link-title3">Link-desription3</a></li>
</ul>
</li>
<li class="mainitem page-item page-item-50">
<a href="link-to-contact" title="title-contact">Contact</a>
</li>
<li class="mainitem page-item page-item-60">
<a href="javascript:void(0);" title="Others">Others</a>
<ul>
<li class="page-item page-item-70"><a href="link-to-submenu-item1" title="link-title1">Link-desription1</a></li>
<li class="page-item page-item-71"><a href="link-to-submenu-item2" title="link-title2">Link-desription2</a></li>
<li class="page-item page-item-72"><a href="link-to-submenu-item3" title="link-title3">Link-desription3</a></li>
</ul>
</li>