Master Pages and Postback in ASP.NET

<asp:UpdatePanel id="MyUpdatePanel" runat="server" ChildrenAsTriggers="True">
  <ContentTemplate>
    ...Stuff you want updated
  </ContentTemplate>
</asp:UpdatePanel>

<asp:UpdatePanel id="MyUpdatePanel" runat="server">
  <ContentTemplate>
    ...Stuff you want updated
  </ContentTemplate>
  <Triggers>
    <asp:AsyncPostBackTrigger ControlID="MyButtonControl" EventName="Click" />
  </Triggers>
</asp:UpdatePanel>