GridView with a single ModalPopupExtender/Panel for row editing

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="Date.ascx.cs" Inherits="controls_Date" %>
<asp:TextBox ID="txtCalendar" runat="server"></asp:TextBox>
<asp:Image ID="imgCalendar" runat="server" ImageUrl="~/App_Themes/default/images/Calendar.png" style="cursor:hand;"/>
<ajaxToolKit:CalendarExtender ID="CalendarExtender1" runat="server" Format="MM/dd/yyyy" PopupButtonID="imgCalendar" TargetControlID="txtCalendar">
</ajaxToolKit:CalendarExtender>
<ajaxToolKit:MaskedEditExtender ID="MaskedEditExtender1"  runat="server" TargetControlID="txtCalendar" ClearMaskOnLostFocus="false" Mask="99/99/9999" MaskType="Date" AutoComplete="true">
</ajaxToolKit:MaskedEditExtender>