See Multiple UpdateProgress Controls?

I have an application where I have multiple gridviews on same page and when I load the gridviews I need to show UpdateProgress control for each one. Since I am using external triggers I am trying to show the UpdateProgress control in Java Script. But it is now working for me. I have attached code snippet and maybe someone will be able to assist me:

<script type="text/javascript">
window.onload = function() {
var prm = Sys.WebForms.PageRequestManager.getInstance();
if (prm != null) {
prm.add_beginRequest(function(sender, args) {
var gridView = document.getElementById("<%=GridView2.ClientID&nbsp;%>");
if (gridView != null) {
document.getElementById("<%=GridView2.ClientID&nbsp;%>").style.display = 'none';
}
var pbControl = null;
pbControl = args.get_postBackElement();
if (pbControl.id == "ctl00_ContentPlaceHolder1_TabContainer1_TabPanel1_DropDownList3") {
alert("DropDownList3 - is the post back element");
document.getElementById("<%=UpdateProgress1.ClientID&nbsp;%>").style.display = '';
}
});
prm.add_endRequest(function(sender, args) {
document.getElementById("<%=GridView2.ClientID&nbsp;%>").style.display = '';
});
}
}
</script>
<cc1:TabContainer ID="TabContainer1" runat="server" Height="20px" ActiveTabIndex="0">
<cc1:TabPanel ID="TabPanel1" runat="server" HeaderText="Current Shift" Style="font-size: xxx-small...................