I'm using Update Progress and when I click in the DropDownList, the progress controls shows up till GridView is filled. So far good. Now, if I do another selection in the DropDownList the GridView stays on the screen as the progress control is beings shown.

How can I prevent the GridView being shown till a new binding taken place? Thank you.

Code:
<cc1:TabContainer ID="TabContainer1" runat="server" Height="20px" ActiveTabIndex="0">
                    <cc1:TabPanel ID="TabPanel1" runat="server" HeaderText="Current Shift" Style="font-size: xxx-small"
                        BackColor="AliceBlue">
                        <HeaderTemplate>
                            Current Shifts
                        </HeaderTemplate>
                        <ContentTemplate>
                            <br />
                            <div style="height: 30px; left: 4px; top: 30px; width: 516px; position: absolute;
                                background-color: #ffffcc; z-index: 102;">
                                <asp:Label ID="Label1" runat="server" Style="top: 6px; left: 7px; position: absolute;
                                    z-index: 100;" CssClass="labellayout" Text="Plant:" />
                                <asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True" CssClass="dropdownlistlayout"
                                    Style="width: 140px; top: 5px; left: 37px; position: absolute; z-index: 101;"
                                    OnSelectedIndexChanged="DropDownList3_SelectedIndexChanged">
                                </asp:DropDownList>
                                <asp:Button ID="Button4" runat="server" CssClass="buttonlayout" Style="left: 476px;
                                    top: 6px;" Text="Export" Width="36px" />
                            </div>
                            <asp:Panel ID="Panel4" runat="server" CssClass="panellayout" Style="top: 60px; height: 201px;
                                width: 518px; left: 2px;" BorderColor="Transparent">
                                <asp:UpdatePanel ID="UpdatePanel2" runat="server">
                                    <Triggers>
                                        <asp:AsyncPostBackTrigger ControlID="TabContainer1$TabPanel1$DropDownList3" EventName="SelectedIndexChanged" />
                                    </Triggers>
                                    <ContentTemplate>
                                        <asp:UpdateProgress ID="UpdateProgress1" runat="server">
                                            <ProgressTemplate>
                                                <br />
                                                <asp:Image ID="Image1" runat="server" ImageUrl="Icons/ajax-loader.gif" />
                                                <asp:Label ID="Label1" runat="server" CssClass="labellayout1" Text="Loading data...."></asp:Label>
                                            </ProgressTemplate>
                                        </asp:UpdateProgress>
                                        <asp:GridView ID="GridView2" runat="server" CssClass="gridviewlayout1" Style="overflow: hidden;
                                            clip: rect(auto auto auto auto); left: 3px; position: absolute; top: 5px" Width="512px"
                                            AllowPaging="True" AllowSorting="True" Font-Size="X-Small" AutoGenerateColumns="False"
                                            CellSpacing="2" HorizontalAlign="Left" BorderColor="LightGray" BorderStyle="None"
                                            PageSize="6" EmptyDataText="No Records Found" Height="19px" ShowFooter="True">
                                            <Columns>
                                                <asp:BoundField DataField="plant_id" HeaderText="Plant" SortExpression="plant_id">
                                                    <ItemStyle Width="25px" HorizontalAlign="Left" />
                                                </asp:BoundField>
                                                <asp:BoundField DataField="plant_name" HeaderText="Plant Name" SortExpression="plant_name">
                                                    <ItemStyle Width="100px" HorizontalAlign="Left" />
                                                </asp:BoundField>
                                                <asp:BoundField DataField="shift_date" HeaderText="Shift Date" SortExpression="shift_date">
                                                    <ItemStyle Width="100px" HorizontalAlign="Left" />
                                                    <FooterStyle HorizontalAlign="Right" Width="40px" />
                                                </asp:BoundField>
                                                <asp:BoundField DataField="outside_qty" HeaderText="Outside Qty" DataFormatString="{0:#,0.00}">
                                                    <ItemStyle Width="45px" HorizontalAlign="Right" />
                                                    <FooterStyle HorizontalAlign="Right" Width="40px" />
                                                </asp:BoundField>
                                                <asp:BoundField DataField="intercompany_qty" HeaderText="Intercomp Qty" DataFormatString="{0:#,0.00}">
                                                    <ItemStyle Width="45px" HorizontalAlign="Right" />
                                                    <FooterStyle HorizontalAlign="Right" Width="40px" />
                                                </asp:BoundField>
                                            </Columns>
                                            <HeaderStyle BackColor="#FFC080" Height="25px" />
                                            <AlternatingRowStyle BackColor="#FFFFCC" />
                                            <RowStyle Height="20px" />
                                            <PagerStyle BackColor="#E0E0E0" />
                                            <EmptyDataRowStyle ForeColor="ActiveCaption" />
                                            <FooterStyle BackColor="#FF8080" Height="20px" HorizontalAlign="Right" />
                                        </asp:GridView>
                                    </ContentTemplate>
                                </asp:UpdatePanel>
                            </asp:Panel>
                        </ContentTemplate>
                    </cc1:TabPanel>