Opening JQuery Ui Dialog in MousePosition

i want to open JQuery UI Dialog In Mouse Position. what is the problem with my code?

<script type="text/javascript">

    $(document).ready(function () {
        var x;
        var y;
        $(document).mousemove(function (e) {
            x = e.pageX;
            y = e.pageY;
        });

        $("#d").dialog({
            autoOpen: false,
            show: "blind",
            hide: "explode",
            position: [x, y]
        });
        $("#c").bind("mouseover", function () {
            $("#d").dialog('open'); // open
        });


        $("#c").bind("mouseleave", function () {
            $("#d").dialog('close'); // open
        });



    });



</script>