This message, posted by either a client or server application, terminates a conversation.
wParam
Identifies the sending window.
lParam
Is reserved.
Posting
Post the WM_DDE_TERMINATE message by calling the PostMessage function, not SendMessage.
While waiting for confirmation of the termination, the sending application should not acknowledge any other messages sent by the receiving application. If the sending application receives messages (other than WM_DDE_TERMINATE) from the receiving application, it should delete any atoms or shared memory objects accompanying the messages.
Receiving
Respond by posting a WM_DDE_TERMINATE message.