Update Panel Not Working - ASP.NET

Hey all,

This is my first post so hope everyone is ok and keen to help a person just joined!

I have added an update Panel around my Table and added a trigger button, but it seems to always update on post back. 

My requirements are;

• Update on ititial Page Load
• Do not update on PostBack

This is my ASP.NET Code

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager><asp:Button ID="Button1" runat="server" Text="Button" /><asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="False" UpdateMode="Conditional"> <Triggers><asp:PostBackTrigger ControlID="Button1" /></Triggers><ContentTemplate> <asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false" CssClass="Grid" AlternatingRowStyle-CssClass="alt"
        DataKeyNames="UserName" OnRowDataBound="OnRowDataBound"><Columns><asp:TemplateField><ItemTemplate><img alt = "" style="cursor: pointer" src="../images/plus.png" /><asp:Panel ID="pnlOrders" runat="server" Style="display: none"><asp:GridView ID="gvOrders" runat="server" AutoGenerateColumns="false" CssClass = "Grid" OnRowCommand="OnRowCommand">  <Columns><asp:BoundField ItemStyle-Width="150px" DataField="UserID" HeaderText="UserID" /></Columns></asp:GridView></asp:Panel></ItemTemplate></asp:TemplateField><asp:BoundField ItemStyle-Width="200px" DataField="UserName" HeaderText="UserName" /><asp:BoundField ItemStyle-Width="200px" DataField="Access" HeaderText="Access" /><asp:BoundField ItemStyle-Width="200px" DataField="FullName" HeaderText="Name" /></Columns></asp:GridView><br /><br /><br /><br /><script type="text/javascript" src="../jquery/jquery-1.8.3.min.js"></script><script type="text/javascript">$("[src*=plus]").live("click", function () {$(this).closest("tr").after("<tr><td></td><td colspan = '999'>" + $(this).next().html() + "</td></tr>")$(this).attr("src", "../images/minus.png");

            });

            $("[src*=minus]").live("click", function () {$(this).attr("src", "../images/plus.png");$(this).closest("tr").next().remove();
            });</script></ContentTemplate> </asp:UpdatePanel> 

On my page i have added the background code in VB.NET

        If Not IsPostBack Then

            Dim strSQL As String
            strSQL = "SELECT UserName, UserName, Access, FullName "
            strSQL = strSQL & "FROM TblDefaultUsers "

            gvCustomers.DataSource = GetData(strSQL)
            gvCustomers.DataBind()

        End If

Any ideas.

Thank you

Jason