<asp:gridview ID="Gridview1" runat="server" ShowFooter="true" Width="100%"
AutoGenerateColumns="false" GridLines="Both" CssClass="mGrid">
<Columns>
<asp:TemplateField ItemStyle-CssClass="cell" HeaderStyle-CssClass="cell" HeaderText="Date Of Travel">
<ItemTemplate>
<asp:TextBox ID="TextBox1" CssClass="txtbox" runat="server"></asp:TextBox>
<asp:CalendarExtender ID="CalendarExtender1" OnClientDateSelectionChanged="checkDate" runat="server" TargetControlID="TextBox1" Format="dd/MM/yyyy">
</asp:CalendarExtender>
</ItemTemplate>
</asp:TemplateField>