Script to lookup data not working

We need to pull data from an internal system. I set-up an asp page to write the required xml out when queried, and wrote a script to link to a button to grab the data from the xml and write it to the form.

It is not working

Script

 var xmlHttp    function showPartData()  {   xmlHttp=GetXmlHttpObject();  if (xmlHttp==null)    {    alert ("Your browser does not support AJAX!");    return;    }  var url="http://www.newpiper.net/rss_data/partdata.asp";  url=url+"?BAAN_SALES_ORDER_NUM="+document.main_form.custrecord_baan_sales_order_number.value;  url=url+"&PART_NUM="+document.main_form.custrecord_part_number.value;  xmlHttp.onreadystatechange=stateChanged;  xmlHttp.open("GET",url,true);  xmlHttp.send(null);  }    function stateChanged()   {   if (xmlHttp.readyState==4)  {  var xmlDoc=xmlHttp.responseXML.documentElement;  document.main_form.custrecord_part_desc.value=xmlDoc.getElementsByTagName("ITEM_DESC")[0].childNodes[0].nodeValue;  document.main_form.custrecord_part_dealer_net.value=xmlDoc.getElementsByTagName("PRICE_CALC_DEALER_NET_PRICE")[0].childNodes[0].nodeValue;  document.main_form.custrecord_part_cost.value=xmlDoc.getElementsByTagName("PRICE_CALC_STD_COST_PRICE")[0].childNodes[0].nodeValue;  document.main_form.custrecord_part_list.value=xmlDoc.getElementsByTagName("PRICE_CALC_LIST_PRICE")[0].childNodes[0].nodeValue;  document.main_form.custrecord_part_operator.value=xmlDoc.getElementsByTagName("PRICE_CALC_OPERATOR_NET_PRICE")[0].childNodes[0].nodeValue;  }  }    function GetXmlHttpObject()  {  var xmlHttp=null;  try    {    // Firefox, Opera 8.0+, Safari    xmlHttp=new XMLHttpRequest();    }  catch (e)    {    // Internet Explorer    try      {      xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");      }    catch (e)      {      xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");      }    }  return xmlHttp;  }