How to hide an items of drop-down list?

"We should not be able to choose some steps of Opportunity History, if the opportunity has no quotes or sales orders." - that was they said.

And that was I wrote.

var oService = null;
var oppid = null;

function FormOnLoad()
{
 oService = new Ascentium_CrmService(null, null);
 
 var oParentCrmForm = window.opener.parent.document.all.crmForm;
 if(oParentCrmForm)
 { 
  oppid = oParentCrmForm.ObjectId;
 }
 
 HideComboboxItems();
}


window.HideComboboxItems = function()
{
var newstep = document.getElementById("new_step");
if(newstep)
{
 // checking opportunity for quotes
 var sFetchXml ='<fetch mapping="logical" aggregate="true" version="1.0"><entity name="quote"><attribute name="quoteid" aggregate="count" alias="count" />'+
  '<filter><condition attribute="opportunityid" operator="eq" value="'+oppid+'" /></filter></entity></fetch>';
 
 var aoFetchResult = oService.Fetch(sFetchXml); 
 var quoteCount = 0;

    if(aoFetchResult.length > 0)
    {
       quoteCount = aoFetchResult[0].attributes["count"].value;
    }
 
 // if no qoutes, then hiding items 4,5,6,7 of dropdown list
 if(quoteCount == 0 )
 {
  var allDropDownElements = newstep.childNodes;
  var lastnodevalue = allDropDownElements.length;
  for(var i=lastnodevalue; i >= 4; i--)
  {
    newstep.options.remove(i);
  }
 }
 else
 {
  // if there is some qoutes, then checking for salesorders
  var sFetchXml ='&lr;fetch mapping="logical" aggregate="true" version="1.0"><entity name="salesorder"><attribute name="salesorderid" aggregate="count" alias="count" />'+
   '<filter><condition attribute="opportunityid" operator="eq" value="'+oppid+'" /></filter></entity></fetch>';
  
  var aoFetchResult = oService.Fetch(sFetchXml); 
  var SOCount = 0;

  if(aoFetchResult.length > 0)
  {
     SOCount = aoFetchResult[0].attributes["count"].value;
  }
  
  // if no salesorders, then hiding items 6,7
  if(SOCount == 0)
  {
   var allDropDownElements = newstep.childNodes;
   var lastnodevalue = allDropDownElements.length;
   for(var i=lastnodevalue; i >=6; i--)
   {
     newstep.options.remove(i);
   }
  }
 }
 
}
}