var popped;
function reservas(codigo) {

        uri = 'calendar.php?codigo='+codigo;
        var params;
        if (popped && !popped.closed) {
                popped.location.href = uri;
                popped.focus();
        } else {
                params = "top=150, left=400, width=180, height=150, menubar=no, toolbar=no, scrollbars=no, resizable=no, status=no";
                popped = window.open(uri, "popup", params);
        }
}