Update Progress Bar Dynamic Change Label

<asp:UpdateProgress ID="updateProgress" runat="server">

<ProgressTemplate>
<asp:Label ID="LblHolder" runat="server" ForeColor="blue" CssClass="lblMsg">

Please wait while processing...

</asp:Label>

</ProgressTemplate>

</asp:UpdateProgress>

<script language="javascript" type="text/javascript">

var prm = Sys.WebForms.PageRequestManager.getInstance();

prm.add_initializeRequest(InitializeRequest);

function InitializeRequest(sender, args)
{

// Get a reference to the element that raised the postback,

// and disables it.

$get(args._postBackElement.id).disabled = true;$get('LblHolder).innerHTML= = "This is a test";


}