function nuevoAjax(){
	var xmlhttp=false;
 	try {
 		xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
 	} catch (e) {
 		try {
 			xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
 		} catch (E) {
 			xmlhttp = false;
 		}
  	}

	if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
 		xmlhttp = new XMLHttpRequest();
	}
	return xmlhttp;
}

function cambio(){
	
	document.getElementById('resultado').innerHTML = '<img src=\"http://xurrency.com/images/cargando.gif\" alt=\"*\" /><img src=\"http://xurrency.com/images/cargando.png\" alt=\"Cargando\" />';
	var base;
	var cambia;
	var amount;
	base = document.getElementById('base').value;
	cambia = document.getElementById('cambia').value;
	amount = document.getElementById('amount').value;
	ajax = nuevoAjax();
	ajax.open("POST", "http://xurrency.com/calculadora",true);
	ajax.onreadystatechange=function() {
		if (ajax.readyState==4) {
			document.getElementById('resultado').innerHTML = ajax.responseText
	 	}
	}
	ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
	ajax.send("base="+base+"&cambia="+cambia+"&amount="+amount)
}