How to use a user-defined message

1. Create a user-defined message with ::RegisterWindowMessage like this:

   
   
   
   const UINT msgFileChange = ::RegisterWindowMessage("FILECHANGE");

   Put this in the application's header file so that you can use this everywhere in your application

2. In your document-class, create a member-variable to hold a pointer to the window you want to process the message.

3. CView *m_pView;
   // This variable must be initialized in your view-class.

4. In the method called by the thread, post the message to the processing window.

   
   
   
   // You can pass wparam, lparam if you wish
   m_pView->PostMessage(msgFileChange);

5. In the processing view header file, add the following in the message map functions:

   
   
   
   // when you pass wparam, lparam add parameters to this function
   afx_msg void OnFileChange();

6. In the processing view source file, add the following in the message map:

7. ON_REGISTERED_MESSAGE(msgFileChange, OnFileChange)

8. Add the source code for OnFileChange in the processing view source file.

   
   
   
   void CProcessView::OnFileChange()
   {
       CMyDocument *pDoc = GetDocument();
       pDoc->UpdateAllViews();
   }

From : http://www.codeproject.com/KB/files/filechange.aspx