Intergration fckeditor with AJAX

Hi, I know this issue has been around for ages here, but I have looked through many posts here, and I still cannot find the solution for my fckeditor and ajax problem, here is the simplified code, please let me know if anyone of you know how to get around this.

Many thanks,
Lau

#############

AJAX function

<script>
function getXMLHttpRequestObject()
{
    if(window.XMLHttpRequest) return new window.XMLHttpRequest();
    else if(window.ActiveXObject) return new window.ActiveXObject("Msxml2.XMLHTTP"); 
    else return new window.ActiveXObject("Microsoft.XMLHTTP");
    return 0;
}

function post(form,url,target)
{
var formdata = "";
xmlhttp = getXMLHttpRequestObject();
for (i=0; i < thisform.length; i++)
    {
   if(thisform.elements[i].type == "text")
      { //Handle Textbox's
      formdata = formdata + thisform.elements[i].name + "=" + escape(thisform.elements[i].value) + "&";
      }
   else if(thisform.elements[i].type == "textarea")
      { //Handle textareas
      formdata = formdata + thisform.elements[i].name + "=" + escape(thisform.elements[i].value) + "&";
      }
   else if(thisform.elements[i].type == "checkbox")
      { //Handle checkbox's
      formdata = formdata + thisform.elements[i].name + "=" + thisform.elements[i].checked + "&";
      }
   else if(thisform.elements[i].type == "radio")
   { //Handle Radio buttons
   if(thisform.elements[i].checked==true)
      {
      formdata = formdata + thisform.elements[i].name + "=" + thisform.elements[i].value + "&";
      }
   }
   else
      {
      formdata = formdata + thisform.elements[i].name + "=" + escape(thisform.elements[i].value) + "&";
      }
    }
xmlhttp.onreadystatechange = function()
   {
   var wait = document.getElementById(target);
   wait.innerHTML = '<div id=\"ajax_loader\"><table border=\"0\"><tr><td><img src=\"img_iconies/ajax_loader_search.gif\"> </td><td> Processing... please wait.</td></tr></table><div>';
   if ((xmlhttp.readyState == 4) && (xmlhttp.status == 200)) 
      {
      var request_response = document.getElementById(target);
      request_response.innerHTML = xmlhttp.responseText;
      }
    }
xmlhttp.open("POST", url);
xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xmlhttp.send(formdata);
return false;
}