In AJAX partial update of the page so ListBox1 only will be updated not the whole page

I have some SQL code I want to run when Timer2 fires. 

How do I do this in the AJAX partial update of the page so ListBox1 only will be updated not the whole page?

<asp:UpdatePanel ID="UpdatePanel2" runat="server"><Triggers><asp:AsyncPostBackTrigger ControlID="Timer2" EventName="Tick" /></Triggers><ContentTemplate><asp:Timer ID="Timer2" Interval="30000" runat="server"></asp:Timer><asp:ListBox ID="ListBox1" Width="500" Height="100" runat="server"></asp:ListBox></ContentTemplate></asp:UpdatePanel>