afx_msg void OnSetFocus( CWnd* pOldWnd );
pOldWnd
Contains the CWnd that loses the input focus (may be NULL). The pointer may be temporary, and should not be stored for later use.
Called after gaining the input focus. To display a caret, CWnd should call the appropriate caret functions at this point.
This message-handler member function calls the Default member function. Override this member function in your derived class to handle the WM_SETFOCUS message.
CWnd::Default, WM_SETFOCUS