var req;
var dest;
function loadXMLDoc(url,valor,valor2,valor3)
{
		dest=valor3;
		req = null;
    // Procura por um objeto nativo (Mozilla/Safari)
    if (window.XMLHttpRequest) {
       	req = new XMLHttpRequest();
		} else if (window.ActiveXObject) {
        req = new ActiveXObject("Microsoft.XMLHTTP");		
		}
   	req.open("GET",url+'?valor='+valor+'&valor2='+valor2, true);
		req.onreadystatechange = processReqChange;
		req.send(null);
				
		<!-- Inicio Envio dados através de post --->
		//req.open("POST",url, true);
		//req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;");
		//req.setRequestHeader("Cache-Control", "no-store, no-cache, must-revalidate");
		//req.setRequestHeader("Pragma", "no-cache");
		//req.onreadystatechange = processReqChange;
    //req.send('valor='+valor+'&valor2='+valor2);
		<!-- Fim Envio dados através de post --->
}

function processReqChange()
{

	// apenas quando o estado for "completado"  
    if (req.readyState == 4) {
      // apenas se o servidor retornar "OK"
      if (req.status == 200) {
				document.getElementById(dest).innerHTML = req.responseText;
			} else {
        alert("Houve um problema ao obter os dados:\n" + req.statusText);
      }
			document.getElementById('carregando').innerHTML = "";
    }else{
			document.getElementById('carregando').innerHTML = "<table width='150' border='0' cellpadding='0' cellspacing='0' bgcolor='#FFFFFF'><tr><td align='center' valign='top'><font color='#333333' size='2' face='Verdana, Arial, Helvetica, sans-serif'>Aguarde, carregando</font></td></tr><tr><td height='30' align='center' valign='middle'><img src='pics/loading.gif' width='70' height='10' /></td></tr></table>";
		}
}
function Atualiza(valor,valor2,valor3,valor4)
{
	loadXMLDoc(valor4,valor,valor2,valor3);
}