Display Grand Total in TextBox outside GridView using jQuery in ASP.Net

I am trying to display grand total of Total Column of gridview in textbox(txtTotal) which is out side of Gridview, but result is not coming.

here is used Jave Script for grand Total.

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () { 
        //Calculate and update Grand Total.
        var grandTotal = 0;
        $("[id*=lblProductTotal]").each(function () {
            grandTotal = grandTotal + parseFloat($(this).html());
        });
        $("[id*=txtTotal]").html(grandTotal.toString());
    });
</script>

Please Guide.