function ajax(URL,PostVars,PostBackFunction)
{
var xmlHttp;
try
  {
  // Firefox, Opera 8.0+, Safari
  xmlHttp=new XMLHttpRequest();
  }
catch (e)
  {
  // Internet Explorer
  try
    {
    xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
    }
  catch (e)
    {
    try
      {
      xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    catch (e)
      {
      alert("Your browser does not support AJAX!");
      return false;
      }
    }
  }
  xmlHttp.onreadystatechange=function()
    {
    if(xmlHttp.readyState==4)
      {
        PostBackFunction(xmlHttp.responseText);
      }
    }
  xmlHttp.open("POST",URL,true);
  xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
  xmlHttp.send(PostVars);
}


// DOM Select element
function insertOptionBeforeSelected(id,value,text)
{
  var elSel = document.getElementById(id);
  if (elSel.selectedIndex >= 0) {
    var elOptNew = document.createElement('option');
    elOptNew.text = text;
    elOptNew.value = value;
    var elOptOld = elSel.options[elSel.selectedIndex];  
    try {
      elSel.add(elOptNew, elOptOld); // standards compliant; doesn't work in IE
    }
    catch(ex) {
      elSel.add(elOptNew, elSel.selectedIndex); // IE only
    }
  }
}

function removeOptionSelected(id)
{
  var elSel = document.getElementById(id);
  var i;
  for (i = elSel.length - 1; i>=0; i--) {
    if (elSel.options[i].selected) {
      elSel.remove(i);
    }
  }
}

function appendOptionLast(id,value,text)
{
  var elOptNew = document.createElement('option');
  elOptNew.text = text;
  elOptNew.value = value;
  var elSel = document.getElementById(id);

  try {
    elSel.add(elOptNew, null); // standards compliant; doesn't work in IE
  }
  catch(ex) {
    elSel.add(elOptNew); // IE only
  }
}

function removeOptionLast(id)
{
  var elSel = document.getElementById(id);
  if (elSel.length > 0)
  {
    elSel.remove(elSel.length - 1);
  }
}

function removeAllOptions(id)
{
  var elSel = document.getElementById(id);
  while(elSel.options.length > 0){
    removeOptionLast(id);
  }
}