see the code

Code:
<div id="list" class="right_txt_space_accm">
											<table width="100%" border="0" cellspacing="0" cellpadding="0">
											  <tr>
												<td  align="left"><strong></strong>
                                                    <asp:CheckBoxList ValidationGroup="testGroup" RepeatColumns=3 RepeatDirection=Horizontal ID="CheckBoxList1" runat="server">
                                                        <asp:ListItem Value="1">Cutomer Broker</asp:ListItem>
                                                        <asp:ListItem Value="2">N.V.O.C.C</asp:ListItem>
                                                        <asp:ListItem Value="3">Hauloiers</asp:ListItem>
                                                        <asp:ListItem Value="4">Air Freight</asp:ListItem>
                                                        <asp:ListItem Value="5">Sea Freight</asp:ListItem>
                                                        <asp:ListItem Value="6">Supply Chain Management</asp:ListItem>
                                                        <asp:ListItem Value="7">Groupage Services</asp:ListItem>
                                                        <asp:ListItem Value="8">Project Cargo</asp:ListItem>
                                                        <asp:ListItem Value="9">Ware House Operator</asp:ListItem>
                                                    </asp:CheckBoxList>
                                                    </td>
												
											  </tr>
                                                
											</table>
										</div>
										<div style="display:none;">
										<table>
										<tr>
										<td> 
										  <asp:TextBox ID="txtcheckbox"  ValidationGroup="testGroup"  runat="server"></asp:TextBox>
                                                    <asp:RequiredFieldValidator ID="valCheckboxlist" runat="server" ValidationGroup=testGroup EnableClientScript=true ControlToValidate =txtcheckbox  ErrorMessage="RequiredFieldValidator">*</asp:RequiredFieldValidator>
                                             </td>
										</tr>
										</table>
										</div>
and script is as
Code:
 <script type="text/javascript">
       

           $(function() {
           function checkboxclicked() {
           var n = $("# list input:checked").length);
           $("input:#txtcheckbox").val(n==0 ? "" : n);
           }
           $(":checkbox").click(checkboxclicked) ;        
           
                     
           });
           
       }</script>
i need to validate the checkbox list(at least one checkbox is selected but its not doing any thing) ,can any one help me