User Control with multiple events has asynchronous postback on event not specified in an UpdatePanel

Question

I have a user control which has two events. A button Click and a drop down list SelectedIndexChanged. Also on the same page there is an UpdatePanel, which has an AsyncPostBackTrigger that is conditional on only one of these events; however, an asynchronous postback occurs when either of the events in the user control occur. Is there a way to have the button Click postback and the drop down list SelectedIndexChanged asynchronously postback?

MyUserControl has:

public event EventHandler TicketSearch;
public event EventHandler CountryChanged;

aspx page has:

<uc1:MyUserControl ID="uc1" runat="server" />
<asp:UpdatePanel ID="up" runat="server" ChildrenAsTriggers="false" UpdateMode="Conditional">
    <ContentTemplate>
     <asp:Label ID="lbl" runat="server" />
    </ContentTemplate>
    <Triggers>
     <asp:AsyncPostBackTrigger ControlID="uc1" EventName="CountryChanged" />
    </Triggers>
</asp:UpdatePanel>