void MDIMaximize( CWnd* pWnd );
pWnd
Points to the window to maximize.
Maximizes an MDI child window. When a child window is maximized, Windows resizes it to make its client area fill the client window. Windows places the child window's Control menu in the frame's menu bar so that the user can restore or close the child window, and adds the title of the child window to the frame-window title.
WM_MDIMAXIMIZE, CMDIFrameWnd::MDIRestore