CalendarExtender not maintaining position in DataList within scrollable div

<pre lang="HTML">
  <div style="z-index:999999">
                                                <asp:TextBox runat="server" ID="txtDOI" Text='<%#Eval("mydt") %>' Width="70px"></asp:TextBox>
                                              <ajaxToolkit:CalendarExtender ID="CalendarExtender2" TargetControlID="txtDOI" Format="dd-MM-yyyy" PopupPosition="Right"
                                                     runat="server">
                                                </ajaxToolkit:CalendarExtender></div>