How Do I Declare Varible In Javascript For Asp.Net Label Control for read filename

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C#

ASP.NET

Javascript

jQuery

I wan't to refresh the javascript code for file which is stored in label control of asp.net,I have tried to declare javascript variable for asp.net control ,but it gives syntax error and this code does not load when project run.
My code is

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js"></script>

<script type="text/javascript">
        // jQuery Document
        alert("hi");
        $(document).ready(function ()
        {
        alert("hi");
            setInterval(loadLogRefresh, 10000);
            //If user wants to end session
            $("#exit").click(function () {
                var exit = confirm("Are you sure you want to exit?");
                if (exit == true) { window.location = 'Logout.aspx'; }
            });
        });

        function loadLogRefresh()
        {
            var oldscrollHeight = $("#chatboxRefresh").attr("scrollHeight") - 20; //Scroll height before the request
            $.ajax({
                var Filename = document.getElementById("lblFileName").value;
                url: Filename;
                cache: false;
                success: function(html)
                {
                $("#chatboxRefresh").html(html); //Insert chat log into the #chatboxRefresh div

                //Auto-scroll
                var newscrollHeight = $("#chatboxRefresh").attr("scrollHeight") - 20; //Scroll height after the request
                if(newscrollHeight > oldscrollHeight)
                    {
                        $("#chatboxRefresh").animate({ scrollTop: newscrollHeight }, 'normal'); //Autoscroll to bottom of div
                    }
                },
            });
        });
</script>