Dynamics CRM 4.0 dynamically populate a picklist from Fetch XML

//Dynamically populate varchar new_itemnumber as a picklist
function SetItems() {
var invid = crmForm.all.new_invoiceid.DataValue;
var xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>";
xml += "<soap:Envelope xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">";
xml += GenerateAuthenticationHeader();
xml += " <soap:Body>";
xml += " <RetrieveMultiple xmlns=\"http://schemas.microsoft.com/crm/2007/WebServices\">";
xml += " <query xmlns:q1=\"http://schemas.microsoft.com/crm/2006/Query\" xsi:type=\"q1:QueryExpression\">";
xml += " <q1:EntityName>invoicedetail</q1:EntityName>";
xml += " <q1:ColumnSet xsi:type=\"q1:ColumnSet\">";
xml += " <q1:Attributes>";
xml += " <q1:Attribute>productid</q1:Attribute>";
xml += "</q1:Attributes>";
xml += "</q1:ColumnSet>";
xml += "<q1:Distinct>false</q1:Distinct>";
xml += "<q1:Criteria>";
xml += "<q1:FilterOperator>And</q1:FilterOperator>";
xml += "<q1:Conditions>";
xml += "<q1:Condition>";
xml += "<q1:AttributeName>invoiceid</q1:AttributeName>";
xml += "<q1:Operator>Equal</q1:Operator>";
xml += "<q1:Values>";
xml += "<q1:Value xsi:type=\"xsd:string\">" + invid + "</q1:Value>";
xml += "</q1:Values>";
xml += "</q1:Condition>";
xml += "</q1:Conditions>";
xml += "</q1:Criteria>";
xml += "</query>";
xml += "</RetrieveMultiple>";
xml += "</soap:Body>";
xml += "</soap:Envelope>"
var xmlHttpRequest = new ActiveXObject("Msxml2.XMLHTTP");
xmlHttpRequest.Open("POST", "/mscrmservices/2007/CrmService.asmx", false);
xmlHttpRequest.setRequestHeader("SOAPAction", " http://schemas.microsoft.com/crm/2007/WebServices/RetrieveMultiple");
xmlHttpRequest.setRequestHeader("Content-Type", "text/xml; charset=utf-8");
xmlHttpRequest.setRequestHeader("Content-Length", xml.length);
xmlHttpRequest.send(xml);
//alert(xml);
var resultXml = xmlHttpRequest.responseXML;
//alert(resultXml.xml);
var Request = resultXml.getElementsByTagName("BusinessEntity");
if (Request.length == 0)
{
   //alert("Aucune ville n'existe pour ce code postal");
   return null;
}
else
{
   if (Request[0].getElementsByTagName("q1:productid")[0] != null)
   {
     function ProdToPickList()
     {
       ConvertProdTextToPickList("new_itemnumber");
     }
     function ConvertProdTextToPickList(controlId)
     {
       var textControl = document.getElementById(controlId);
       var picklistControl = document.createElement("SELECT");
       picklistControl.id = textControl.id;
       picklistControl.req = textControl.req;
       picklistControl.className = "ms-crm-selectBox";
       AddPickListValues(picklistControl);
       picklistControl.value  = textControl.DataValue;
       textControl.parentElement.appendChild(picklistControl);
       textControl.parentElement.removeChild(textControl);
       }
function AddPickListValues(picklistControl) {
var items = resultXml.selectNodes("//BusinessEntity/q1:productid"); 
if(items != null) 
{ 
for( i = 0; i < items.length; i++) 
{ var option = document.createElement("OPTION"); option.innerText = items[i].text; picklistControl.appendChild(option); 
}
 }
   ProdToPickList();
   }	
 }
}
http://social.msdn.microsoft.com/Forums/en-US/crmdevelopment/thread/4f50b8c7-e9a8-40a6-a26c-76b5dcb9ea14

I modified the code in the above thread to dynamically populate a nvarchar textbox called new_itemnumber as a picklist by selecting the product id's from the InvoiceDetail view based on an existing Invoice Id.  It is not working and I am not getting an error.  Any thoughts?

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GM