怎樣做下拉式的分月？

<li id="archives">過期文章
        <ul>
        <form action="" name="Month" id="Month">
        <select name="menu_month" id="menu_month" onchange="jumpMenu('parent',this,0)">
        <option value="">請選擇月份</option>
         <?php wp_get_archives('format=option'); ?>
         </select>
         </form>
        </ul>
</li>

<script type="text/javascript">
function jumpMenu(targ,selObj,restore){
if(!selObj.options[selObj.selectedIndex].value){
                return false;
         }
eval(targ+".location='"+selObj.options[selObj.selectedIndex].value+"'");        if (restore)
selObj.selectedIndex=0;
}
</script>
怎樣做下拉式的分月