datalist中radiobutton被选中后想取道LABEL里的值怎么做到！

Question

    <script language="javascript">
    function ChangeChk(ctl)
    {
      var theBox=ctl;
      var elem=theBox.form.elements;
      for(i=0;i<elem.length;i++)
        {
            if(elem[i].type=='radio')
            {
               if(elem[i].id==theBox.id)
               {
                  elem[i].checked=true;
               }
               else
               {
                  elem[i].checked=false;
               }
            }
        }
    }
    </script>                    <asp:DataList ID="ListShowBillboard" RepeatDirection="Horizontal" RepeatColumns="3"
                        Width="550" runat="server">
                        <ItemTemplate>
                            <table border="0" cellpadding="0" cellspacing="0" width="183">
                                <tr>
                                    <td align="center">
                                        <asp:Label ID="Label1" runat="server" Text='<%#DataBinder.Eval(Container.DataItem,"id")%>'
                                            Visible="false"></asp:Label>
                                        <img src="../<%#DataBinder.Eval(Container.DataItem, "pict1_file")%>" border="0" />
                                    </td>
                                </tr>
                                <tr>
                                    <td align="center">
                                        <asp:RadioButton ID="Chk1" runat="server" onclick="ChangeChk(this)" AutoPostBack="true"></asp:RadioButton>
                                    </td>
                                </tr>
                            </table>
                        </ItemTemplate>
                    </asp:DataList>

Answer 1

   function ChangeChk(ctl) 
    { 
      var theBox=ctl; 
      alert(theBox.nextSibling.innerHTML); // HERE
// ....