Hello,

I followed the MS instructions to subclass Windows using C#.net
(http://support.microsoft.com/kb/815775) as the follows. I then opened
several Excel files, and selected anyone of them as foreground window. I  was
expecting to see windows message, saying WM_ACTIVATE, or something like that,
however, to my surprise, I saw NO windows message when I randomly selected
those Excel windows, (although I could see other window messages, e.g.,
WM_GETTEXT).

What was wrong here? I need to be able to tell which Excel window is the
active one programmatically. Was this a right approach for this purpose? Any
papers?

Thanks a lot.

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Add a new Class module that is named SubclassHWND.cs to the Visual C# .NET
or Visual C# 2005 application. To do this, click Add Class on the Project
menu.  
2. In the Name text box, type SubclassHWND.cs, and then click Open.
3. Replace the SubclassHWND class code with the following code:public class
SubclassHWND : NativeWindow
 {
  protected override void WndProc(ref Message m)
   {
     // Perform whatever custom processing you must have for this message
     System.Diagnostics.Debug.WriteLine(m.ToString());
    // forward message to base WndProc
    base.WndProc(ref m);
   }
}

4. To demonstrate its use, add the following code to the Load event of
Form1:SubclassHWND s = new SubclassHWND();
s.AssignHandle(this.Handle);
//Now s should be listening to the messages of the form.