Apply the same common mouse conventions for activating and switching between primary windows for MDI child windows. CTRL+F6 and CTRL+TAB (and SHIFT+ modified combinations to cycle backwards) are the recommended keyboard shortcuts for switching between child windows. In addition, include a Window menu on the menu bar of the parent window with commands for switching between child windows and managing or arranging the windows within the MDI parent window — such as Tile or Cascade.
When the user switches child windows, you can change the interface of the parent window — such as its menu bar, toolbar, or status bar — to appropriately reflect the commands that apply to that child window. However, provide as much consistency as possible, keeping constant any menus that represent the document files and control the application or overall parent window environment, such as the File menu or the Window menu.