Concurrent call to a simplemodal object

I have to make a function concurrent to multiple open/close modal requests.

For exemple: When i call showAjaxLoading(true), it's showing the modal, and showAjaxLoading(false) it's disposing the modal.

The Problem: When i make a first long request to showing the modal, and another one quick request will close it. I want to be able keeping in a array all the requests and disposing the modal only when the last request is ended.

SimpleModal: The object simplemodal is unique. When you create the modal it return the object itself. But when you have a modal already open, it returns false. url: http://www.ericmmartin.com/projects/simplemodal/

var showAjaxLoading = function (show) {
    var ajaxModal;
    if (show) {
        var aModal = $("#ajaxLoading").modal({ overlayId: 'ajaxloading-overlay', containerId: 'ajaxloading-container', closeClass: 'ajaxloading-close', close: false, escClose: false });
        if (aModal !== false) {
            ajaxModal = aModal;
        };
    } else {
        if (ajaxModal !== undefined && $.isFunction(ajaxModal.close)) {
            ajaxModal.close();
        };
    };
};

What the is the best solution to solve this problem ?

var modalDialog = {
    _requestsInProcess: 0,

    showAjaxLoading : function()
    {
        if ( this._requestsInProcess == 0 )
        {
            // open overlay here
        }

        this._requestsInProcess++;
    },

    hideAjaxLoading : function()
    {
        this._requestsInProcess--;
        if ( this._requestsInProcess == 0 )
        {
            // hide overlay here
        }
    }
}

Try something like this/ Now you can call modalDialog.showAjaxLoading() each time you making AJAX request and modalDialog.hideAjaxLoading() each time your request is completed.