求ajax实现的select与checkbox的联动代码或方法

<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<script type="text/javascript">
var httpRequest;
function createXMLHttp()
{
    if(window.ActiveXObject)
httpRequest = new ActiveXObject("MicroSoft.XMLHTTP");
    else if(window.XMLHttpRequest)
httpRequest = new XMLHttpRequest();
}
function GetStudents()
{
    createXMLHttp();
    var strURL="http://localhost/TestWebSite/GetStudents.aspx?class="+slctClass.value;    //可以返回数据的服务端页面
    httpRequest.onreadystatechange=onGetReady;
    httpRequest.open("GET",strURL,true);
    httpRequest.send(null);
}
function onGetReady()
{
    if(httpRequest.readyState == 4 && httpRequest.status == 200)
    {
        var nStudents=httpRequest.responseXML.selectNodes("/Students/Student");
        divStudents.innerHTML="";
var strStudents="<table><tr>";
for(var i=0;i<nStudents.length;i++)
{
var nStudent=nStudents[i];
strStudents+="<td><input type='checkbox' id='chbStudent"+i+"' value='"+nStudent.text+"'/>"+nStudent.text+"</td>";
}
strStudents+="</tr></table>";
divStudents.innerHTML=strStudents;
    }
}
</script>
</HEAD><BODY>
<select id="slctClass" onchange="GetStudents()">
<option value="1">一班</option>
<option value="2">二班</option>
<option value="3">三班</option>
</select>
<div id="divStudents"></div>
</BODY>
</HTML>后台http://localhost/TestWebSite/GetStudents.aspx页面返回的XML格式：
  <?xml version="1.0" encoding="gb2312" ?> 
  <Students>
    <Student>张三</Student> 
    <Student>李四</Student> 
    <Student>王五</Student> 
  </Students>