function change_offre(id_prod){
var xhr_object = null;            
if(window.XMLHttpRequest) // Firefox
  xhr_object = new XMLHttpRequest();
else if(window.ActiveXObject) // Internet Explorer
  xhr_object = new ActiveXObject("Microsoft.XMLHTTP");
else { // XMLHttpRequest non supporté par le navigateur
  alert("Votre navigateur ne supporte pas les objets XMLHTTPRequest...");
  return;
}

document.getElementById("dte_offre").innerHTML = '<div align="center"><br><br><br><br><br><br><img src="../img_com/loading.gif" alt="" width="20" height="20" border="0"></div>';

var url="_inc/block_offre.php";
url=url+"?id_prod="+id_prod;
url=url+"&sid="+Math.random();
xhr_object.open("GET",url, true);

xhr_object.onreadystatechange = function() {
  if(xhr_object.readyState == 4)   
	if (xhr_object.responseText =="") {
	document.getElementById("dte_offre").innerHTML = "AUCUNE OFFRE TROUVE";
	}else {
	document.getElementById("dte_offre").innerHTML = xhr_object.responseText;
	}
	//alert (xhr_object.responseText);
}
xhr_object.send(null);
}