showing a hidden panel in OnTextChanged event

I want to show a hidden panel when a user tabs out of a text box. I want to do this asynchronously. I wrote the following code. In below code my <asp:Panel is on another part of the page. Its not right above the updatePanel. I just put the panel above my textbox code for simplicity.

<form id="form1" runat="server" method="post"><asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager><asp:Panel runat="server" ID="pnlTest" Visible="false">
            This is a test</asp:Panel><asp:UpdatePanel ID="up1" runat="server"><ContentTemplate ><asp:TextBox ID="txtTest" runat="server" OnTextChanged="txtestChanged" AutoPostBack="true"></asp:TextBox></ContentTemplate><Triggers><asp:AsyncPostBackTrigger ControlID ="txtTest" /></Triggers></asp:UpdatePanel></form>

any help will be greatly appreciated.