Ajax - Multi carregamento (request) - Solução

	var xhr = new Array(); // ARRAY OF XML-HTTP REQUESTS
	var xi = new Array(0); // ARRAY OF XML-HTTP REQUEST INDEXES
	xi[0] = 1; // FIRST INDEX SET TO 1 MAKING IT AVAILABLE
	
//-----------------------------------------------------------------
// FUNÇÃO AJAX REQUEST
//-----------------------------------------------------------------
function xhrRequest(type) {
	if (!type) { type = 'html'; }
	// xhrsend IS THE xi POSITION THAT GETS PASSED BACK
	// INITIALIZED TO THE LENGTH OF THE ARRAY(LAST POSITION + 1)
	// IN CASE A FREE RESOURCE ISN'T FOUND IN THE LOOP
	var xhrsend = xi.length;	
	// GO THROUGH AVAILABLE xi VALUES
	for (var i=0; i<xi.length; i++) {
		// IF IT'S 1 (AVAILABLE), ALLOCATE IT FOR USE AND BREAK
		if (xi == 1) { xi = 0; xhrsend = i;			
			break;
		}
	}
	// SET TO 0 SINCE IT'S NOW ALLOCATED FOR USE
	xi[xhrsend] = 0;
	// SET UP THE REQUEST
	if (window.ActiveXObject) {
		try {
			xhr[xhrsend] = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			try {
				xhr[xhrsend] = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e) {}
		}
	} else if (window.XMLHttpRequest) {
		xhr[xhrsend] = new XMLHttpRequest();
		if (xhr[xhrsend].overrideMimeType) {
			xhr[xhrsend].overrideMimeType('text/' + type);
		}
	}
	return (xhrsend);
}

	var xhri = xhrRequest('html');
		
	xhr[xhri].onreadystatechange = function(){
	   
       // ação a executar

	};