Hi ,
1.I am having a modeless dialog box(1).
2.On that modeless dialog box i am having a button.
3.On the click of button i am calling a modal dialog box(2).
4.On the modal dialog box there is a button.on the click of this
button i am trying to send user defined messages to the dialog box
(1).
However i found that the messages are never received by the dialog box
(1).
Could anybody please help me in finding a solution for this...

regards
debs

Debs,
        By what are you judging that the messages are never received?  
Have you put TRACE statements in the handlers for the messages?  How did
you declare the message handlers?  Did you remember to put ON_MESSAGE
entries in the message map?

User defined messages are private messages. They are posted to the owning
window only.
Try using ::PostMessage with HWND_BROADCAST as the first parameter.
I had a similar problem and it worked.

???

Messages are sent or posted to the window to which you direct them.  No
window "owns" a message.  There's a sender and a receiver.  In the case
of HWND_BROADCAST, Windows makes ALL top-level windows the receiver.  
Unless you are intending for multiple, unspecified windows to handle
your user message, broadcast is not an appropriate solution.

Is there something wrong in what I said? or is it unclear?

I believe your advice was incorrect, for the reasons I posted last.  
However, there's always the possibility that I just misunderstood you.

Yup,
Thanks for the corrections.