function callAjax(url, controlToUpdate, callBackOK, callBackNOK)
{ 
    var objRequest;
    var objControlToUpdate = document.getElementById(controlToUpdate);
    
    try 
    {
        objRequest = new XMLHttpRequest();
    }
    catch(e) 
    {    
      objRequest = new ActiveXObject(Microsoft.XMLHTTP);
    } 
 
    objRequest.onreadystatechange = function()
    { 
        if(objRequest.readyState  == 4)
        {
            if(objRequest.status  == 200)
            {
                if (objControlToUpdate)
                {
                    objControlToUpdate.innerHTML = objRequest.responseText;
                    objControlToUpdate.style.visibility = 'visible';
                }
                
                if (callBackOK)
                {
                    callBackOK(objRequest.responseText, controlToUpdate, objRequest.status);
                }
            }
            else 
            {
                if (callBackNOK)
                {
                    callBackNOK(objRequest.responseText, controlToUpdate, objRequest.status);
                }
            }
        }
    }; 

   objRequest.open('GET', url, true); 
   objRequest.send(null); 
}