Modal popup checkbok event not fire

Hi,

<asp:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="dummyID"
PopupControlID="divNameList" DropShadow="true" BackgroundCssClass="modalcontent"
Drag="true"  OnLoad="ModalPopupExtender1_Load"
CancelControlID="DivbtnCancel" ></asp:ModalPopupExtender><div id="divNameList" runat="server" style="display: none; position: absolute; border-width: 2px;
                                            border-color: #5a8cbf; top: 30%; left: 20%; margin-left: -25%; margin-top: -25%;
                                            height: 500px; width: 520px;"><div><asp:Button ID="dummyID" runat="server" Width="0px" Style="display: none" /><table border="0" cellpadding="0" cellspacing="0" width="100%"><tr class="tdheading"><td><table><tr class="label"><td style="text-align: left"><asp:Label ID="Label97" runat="server" CssClass="labelheader" Text= "Contact List"></asp:Label></td></tr></table></td></tr><tr><td><div style="overflow-y: auto; height: 460px; width: 520px; background-color: #DEE7F9"><asp:GridView ID="gvNameList" runat="server" Width="100%" AutoGenerateColumns="false"
                            AllowPaging="false" AllowSorting="false" GridLines="Horizontal" CellPadding="0"
                            OnRowDataBound="gvNameList_RowDataBound"><Columns><asp:TemplateField HeaderText="Select" HeaderStyle-HorizontalAlign="Left" HeaderStyle-Width="40px"><ItemTemplate><asp:CheckBox ID="chkSelect" runat="server"  OnCheckedChanged="chkSelect_CheckedChanged"  /><asp:HiddenField ID="HiddenField1" Visible="false" runat="server" /><asp:HiddenField ID="hdnUmID" Visible="false" Value='<%# Bind("um_id") %>' runat="server" /><asp:HiddenField ID="hdnUmLogin" Visible="false" Value='<%# Bind("um_login") %>'
                                            runat="server" /></ItemTemplate></asp:TemplateField><asp:TemplateField HeaderText="Name" HeaderStyle-HorizontalAlign="Left" HeaderStyle-Width="150px"
                                    ItemStyle-Width="150px"><HeaderTemplate><cc2:Filter ID="HTtxtName" HeaderText="Name" runat="server" HeaderCssClass="labelheader"
                                            TextBoxCssClass="inputEnabled" TextBoxWidth="150px" OnClick="FilterSearch_Click"></cc2:Filter></HeaderTemplate><ItemTemplate><asp:Label ID="lblName" runat="server" CssClass="label" Text='<%# Bind("um_name") %>'></asp:Label></ItemTemplate></asp:TemplateField><asp:TemplateField HeaderText="Email" HeaderStyle-HorizontalAlign="Left" HeaderStyle-Width="150px"
                                    ItemStyle-Width="180px"><HeaderTemplate><cc2:Filter ID="HTtxtEmail" HeaderText="Email" runat="server" HeaderCssClass="labelheader"
                                            TextBoxCssClass="inputEnabled" TextBoxWidth="150px" OnClick="FilterSearch_Click"></cc2:Filter></HeaderTemplate><ItemTemplate><asp:Label ID="lblEmail" runat="server" CssClass="label" Text='<%# Bind("um_email_id") %>'></asp:Label></ItemTemplate></asp:TemplateField></Columns><PagerStyle CssClass="gvPager" Font-Size="10pt" HorizontalAlign="Right" /><EmptyDataRowStyle CssClass="gvEmptyDataRow" /><HeaderStyle CssClass="labelheader" HorizontalAlign="Left" VerticalAlign="Top" Height="20px" /><RowStyle CssClass="label gvRowStyle" Height="20px" /><SelectedRowStyle CssClass="gvSelectedRow" /><AlternatingRowStyle CssClass="label gvRowStyle" Height="20px" /></asp:GridView></div></td></tr><tr style="background-color: #DEE7F9"><td align="center" style="padding-right: 5px; width: 1%; cursor: pointer;"><asp:Button ID="btnOk" CssClass="button" Text=" Ok " runat="server" OnClick="btnOk_Click" /><asp:Button ID="DivbtnCancel" CssClass="button" Text="Cancel" runat="server" OnClick="btnNameClose_Click" /></td></tr></table></div></div>

In Codebehind

protected void ModalPopupExtender1_Load(object sender, EventArgs e)
{
Binded the values using data table.
}

when I Click on chkSelect_CheckedChanged event, which is not fired.

Any Idea will appreciate...