Trigger Update Panel from User Control Event

Question

Hello,
 
I am using Update Panel, whose mode is "Conditional".
I have one User Control in which have one drop down and one button.
While selecting the value from Dropdown and click on save button that selected value should be appear on the panel of agency information.
Agency Information panel is in Update Panel whose mode is conditional.
 
How can i trigger agency information panel on user control event.
 
This is my first update panel which i want to update.

<asp:UpdatePanel ID="upAgencyInfo" runat="server" UpdateMode="Conditional">
   <Triggers>
        <asp:AsyncPostBackTrigger ControlID="AssignCaseToUser" EventName = "Click" />
    </Triggers>
    <ContentTemplate>
        <table class="table_border1" width="100%" align="center" border="0" cellpadding="1"
            cellspacing="1" bgcolor="#ffffff"  runat="server">
            <tr class="TableHeader">
                <td height="24" colspan="4" align="left">
                    <span class="blueText"> <asp:Label ID="lblAgencyTitle" runat="server" Text="Agency Information"></asp:Label></span>
                </td>
            </tr>
            <tr>
                <td height="24" class="SearchRowBlue" width="12%">
                    <span class="blackText">
                        <asp:Label ID="lblAgencyType" CssClass="blackText" Text="Auditor Name" runat="server" /></span>
                </td>
                <td height="24" class="SearchRowBlue1" colspan="3" width="42%">
                    <asp:Label ID="lblVendoName" CssClass="LableText" runat="server" />
                </td>
            </tr>
            </table>
    </ContentTemplate>
</asp:UpdatePanel>

This is my second update panel where i put my User control.


<asp:UpdatePanel ID="upAgencyEntry" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        <asp:Panel ID="pnlAssignDesigUser" runat="server" CssClass="modalPopup" Width="40%"
            Style="display: none">
            <AssignCase:AssignCase ID="AssignCaseToUser"  runat="server" />
        </asp:Panel>
    </ContentTemplate>
</asp:UpdatePanel>

Here "AssignCaseToUser" contains "btnSave" and "BtnSave_Click()" event.