Multiple Popunders with capping Javascript

I am using the following JavaScript to open a popunder, but right now it's opening only 1 popunder per cookie session, i.e. 1 popunder for 24 hours, and I want to open 2 popunders per session, i.e. 2 popunders open at the same time.

How do I do that?

<script type="text/javascript" language=javascript>
    function Set_Cookie(name, value, expires, path, domain, secure) {
        var today = new Date();
        today.setTime(today.getTime());
        var expires_date = new Date(today.getTime() + (expires));

        document.cookie = name + "=" + escape(value) +
            ((expires) ? ";expires=" + expires_date.toGMTString() : "") +
            ((path) ? ";path=" + path : "") +
            ((domain) ? ";domain=" + domain : "") +
            ((secure) ? ";secure" : "");
    }

    function Get_Cookie(name) {

        var start = document.cookie.indexOf(name + "=");
        var len = start + name.length + 1;
        if ((!start) &&
            (name != document.cookie.substring(0, name.length))) {
            retu null;
        }
        if (start == -1) retu null;
        var end = document.cookie.indexOf(";", len);
        if (end == -1) end = document.cookie.length;
        retu (document.cookie.substring(len, end));
    }

    function Delete_Cookie(name, path, domain) {
        if (Get_Cookie(name)) document.cookie = name + "=" +
            ((path) ? ";path=" + path : "") +
            ((domain) ? ";domain=" + domain : "") +
            ";expires=Mon, 11-November-1989 00:00:01 GMT";
    }

    function popunder() {

        if (Get_Cookie('cucre') == null) {
            Set_Cookie('cucre', 'cucre Popunder', '1', '/', '', '');
            var url = "http://google.com/";
            pop = window.open(url, 'windowcucre');
            pop.blur();

            window.focus();
        }
    }

    function addEvent(obj, eventName, func) {
        if (obj.attachEvent) {
            obj.attachEvent("on" + eventName, func);
        } else if (obj.addEventListener) {
            obj.addEventListener(eventName, func, true);
        } else {
            obj["on" + eventName] = func;
        }
    }

    addEvent(window, "load", function(e) {
        addEvent(document.body, "click", function(e) {
            popunder();
        });
    });
</script>