CheckBoxlist in web explorer bar.

<ig:WebExplorerBar ID="Test" runat="server" GroupExpandBehavior="AnyExpandable"
StyleSetName="Office2007Blue">
<ClientEvents ItemClick="ItemClickHandler" />
<Groups>
<ig:ExplorerBarGroup Text="Activities">
<Items>
<ig:ExplorerBarItem Text="Child">
<Template>
<asp:CheckBoxList ID="m_chkUMActivities" runat="server" Visible="true" RepeatDirection="Vertical"
RepeatLayout="Flow" TextAlign="Right" OnClick="MaintainingSaveBtnState()">
</asp:CheckBoxList>
</Template>
</ig:ExplorerBarItem>
</Items>
</ig:ExplorerBarGroup>
</Groups>
</ig:WebExplorerBar>

// here I need to get the all check box that are checked in checkboxlist

 function MaintainingSaveBtnState() {

var webExplUM = $find("m_pnlUMActivities");
var checklistUM = webExplUM.getExplorerBarItems().getItem(0).get_textElement()

 var chkBoxCountUM = checklistUM.getElementsByTagName('input'); // but here I always get length as 0. could you please assist in this that how I can get checked element in checkboxlist.

Thanks!!!