Can I just add a messagemap entry..
ON_MESSAGE( WM_USER, OnWmUser )

define my message map function in header file
afx_msg void OnWmUser();

and implement it in the cpp file:
void OnWmUser( )
{
    ...do something spiffy

???

It would seem to easy to be true :-)

Well, it's true that that's about how easy it is, but your implementation
outline has several errors.  Check out this to get the details right:
  http://www.mvps.org/vcfaq/mfc/index.htm

--
Scott McPhillips [VC++ MVP]

Don't use WM_USER, the system itself uses messages in the low WM_USER
range for dialogs (I know, dumb isn't it). Use WM_APP. Better still
use RegisterWindowMessage and ON_REGISTERED_MESSAGE.

You need to follow the correct format for a message handler, with an
LRESULT, a WPARAM and an LPARAM. This is documented in the help on
user defined handlers.

--
Bob Moore [MVP]
http://www.mooremvp.freeserve.co.uk
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Due to an unreasonable amount of queries, I no
longer answer unsolicited email questions. Sorry,
no exceptions, and yes, this DOES mean you.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Check out my essay on user-defined messages on
http://www3.pgh.net/~newcomer/mvp_tips.htm
                        joe

Joseph M. Newcomer

Web: www3.pgh.net/~newcomer
MVP Tips: www3.pgh.net/~newcomer/mvp_tips.htm
Author of "Win32 Programming" (with Brent Rector, Addison-Wesley, 1997)
Author of "Developing Windows NT Device Drivers" (with Ed Dekker, AWL, 1999)