how to call javascript on link button in selected index change of a gridview ?

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C#

Javascript

hi,

My prob is this that i m downloading smething on a click of dwnload button taken in gridview.
for the user freindly scenario I want to add "PLs wait" motion image so that on click of download button till the download button starts user can be notified that please wait the download is starting. I am using this through javascript however on calling this function on link button on cleint click event nothing is happening . Am i doing smethng wrong ? Do i need to call smethng on page load event too ? my code for the function and gridview is given below :-

function plzwait()
{

ProgressImage = document.getElementById('progress_image');
                  setTimeout("ProgressImage.src = ProgressImage.src",100);
                  document.getElementById("divsearch").style.display = 'block';
                  document.getElementById('ctl00_BodyContents_lblsearch').innerHTML = "Data Mining is in Progress, It will Take Time So Please Wait........";

                  }

<asp:GridView ID="gv_WorkOrder" runat="server"  AutoGenerateColumns="False" OnSelectedIndexChanged="gv_WorkOrder_SelectedIndexChanged">
                            <Columns>
                                <asp:TemplateField HeaderText="Work Order Name">
                                    <ItemTemplate>
                                        <asp:Label ID="lblWrkOrder" runat="server" Text='<%# bind("WorkOrder_Name") %>'></asp:Label>
                                    </ItemTemplate>
                                </asp:TemplateField>
                                <asp:TemplateField HeaderText="Download">
                                    <ItemTemplate>
                                        <asp:LinkButton ID="lnkSelect" runat="server" CommandName="Select" OnClientClick = "javascript:plzwait();">Download</asp:LinkButton>
                                    </ItemTemplate>
                                </asp:TemplateField>
                            </Columns>
                        </asp:GridView>