Updating label text several times during click event

Hi All,
I have a simple application that is written in C# using VS2012, in a web forms application. 
There is one button that starts the processing and I would like to give the user updates to the progress of the processing by putting some text in a Label.  I thought I could put the Label control in an UpdatePanel and then during the Button click event trigger the change in the Label text by calling the UpdatePanel Update() method.  However, the only time the label text changes is after the click event completes and the Label text is displayed, 'Process complete'.
This is my xml:
<asp:UpdatePanel ID="ProgressUpdatePanel" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="False"> <ContentTemplate> <div style="height: 81px"> <asp:Label ID="lblCaption" runat="server" CssClass="labe ...