Add querystring to Ajax in classic asp

I have a dynamic page that is displaying details based upon a unique ID being passed in my querystring/url parameter. I'm trying to figure out how to add the querystring to the GET Ajax based upon this unique id.

This what I have:
mypage.asp?id=1

<div id="moreDiv"></div>
<div id="foo">
<h3 class="more"><a href="javascript: void(0)" onclick="toggle_visibility('foo'); loadXMLDoc()"><span>[+]</span> view comments</a></h3>
</div>




<script>
function loadXMLDoc()
{
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }

xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("moreDiv").innerHTML=xmlhttp.responseText;
    }

else {
document.getElementById("moreDiv").innerHTML='<img id="centerload" src="ajax-loader.gif">';
}
}

// I tried this without luck
var myquerystring = window.location.search.substring(1);

xmlhttp.open("GET","commentsmore.asp?id=" + myquerystring,true);
xmlhttp.send();
}
</script>