关于ajax select 无限极联动修改时自动创建并选中时的问题

页面：<tr>
<td>产品名称</td>
<th id="proContent">
                        <select id="proname" name="proname"  onchange="showChild()">
                        <option value="">请选择..</option>
                            <tpl:foreach collection="$PROLIST$" var="PRO" index="i">
                            
                                <tpl:if test="$equals(PRO.ID,CINT(FIRSTPRO))$">
                                    <tpl:set name="select" value="selected='selected'" />
                                    <tpl:else />
                                    <tpl:set name="select" value="" />
                                </tpl:if>
                            <option value="$PRO.ID$" $select$>$PRO.NAME$</option>
                            </tpl:foreach>
                        </select>
</th>
</tr>
下面是js：   function showChild()
   {
   var obj=event.srcElement;
   var currentObj=$$(obj);
   var s1=$$(obj).nextAll("select");
   s1.each(function(i){
   $$(this).remove();
   });
   var value1=$$(obj).val();
      $$.post("/ActionPage/Repertories.aspx?clsid="+value1,function(list){
            eval(list)
            
            if(list.length>0)
            {
                $$("<select id=\"no1"+value1+"\" name=\"proname\" onchange=\"showChild()\" ></select>").appendTo("#proContent");
                $$("<option value=''>请选择..</option>").appendTo("#no1"+value1);
                for (var i = 0; i < list.length; i++) 
                { 
                    document.getElementById("no1"+value1).add(new Option(list[i].name,list[i].proid));                }
            
            }
        }); 
添加的时候可以实现联动。数据库的存的是以1,2，3的形式存放。
请问我修改的时候怎么让它自动创建select并选中呢？