I tried to resolve it by myself, but it is not getting resolved below is JavaScript, which is i am using for calculating total of Gridview last column total but it is two column values in footer,

Second thing if i change any value in GridView, it also must be update txttotal textbox which is outside of GridView

Below is gridview and JS

<script type="text/javascript">
    $(function () {
        //Calculate and update Grand Total.
        var grandTotal = 0;
        $("[id*=lbltotal]").each(function () {
            grandTotal = grandTotal + parseFloat($(this).html());
        });
        $("[id*=txtTotal]").val(grandTotal.toString());
    });
</script>

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:GridView ID="GVFood" Width="97%" PagerStyle-CssClass="pager" HeaderStyle-CssClass="header" ShowFooter="true"
            RowStyle-CssClass="rows" runat="server" AutoGenerateColumns="false" auttopostback="true"
            OnRowEditing="GVFood_RowEditing" OnRowDataBound="GVFood_RowDataBound" OnRowDeleting="GVFood_RowDeleting"
            Height="216px" CssClass="auto-style15">
            <Columns>
                <asp:TemplateField HeaderText="S.No">
                    <ItemTemplate>
                        <%#Container.DataItemIndex+1 %>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:BoundField DataField="B_ID" HeaderText="Codeitem" Visible="false" />
                <asp:BoundField DataField="B_Name" HeaderText="Descriptionitem" ReadOnly="true" />
                <%--<asp:BoundField DataField="QTY" HeaderText="QTY" onkeyup="CalculateTotals();" ControlStyle-Width="20px"  />--%>
                <asp:TemplateField HeaderText="Quantity">
                    <ItemTemplate>
                        <asp:TextBox ID="QTY" Text='<%#Eval("QTY") %>' Enabled="true" AutoPostBack="True" OnTextChanged="QTY_TextChanged" runat="server" ControlStyle-Width="50px"></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Price">
                    <ItemTemplate>
                        <asp:TextBox ID="Rate" runat="server" Width="50px" Enabled="true" AutoPostBack="True" OnTextChanged="Rate_TextChanged" Text='<%#Eval("Rate") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Dis">
                    <ItemTemplate>
                        <asp:TextBox ID="txtdisc" runat="server" AutoPostBack="True" OnTextChanged="txtdisc_TextChanged" Width="50px" Enabled="true" Text='<%#Eval("txtdisc") %>'></asp:TextBox>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="S.Total">
                    <ItemTemplate>
                        <asp:Label ID="lbltotalDisc" runat="server" Text=""></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Total">
                    <ItemTemplate>
                        <asp:Label ID="lbltotal" runat="server" Text='<%# Eval("lbltotal") %>'></asp:Label>
                    </ItemTemplate>
                    <FooterTemplate>
                        <asp:Label ID="lblGrandTotal" runat="server"></asp:Label>
                    </FooterTemplate>
                </asp:TemplateField>
                <asp:CommandField ShowDeleteButton="True" ButtonType="Link" />
            </Columns>
        </asp:GridView>
    </ContentTemplate>
    <Triggers>
    </Triggers>
</asp:UpdatePanel>
Grand Total : 
<asp:TextBox ID="txtTotal" runat="server" Height="19px" Width="58px" Enabled="False"></asp:TextBox>