Application.WindowState (Word)

Returns or sets the state of the specified document window or task window. Possible return values are wdWindowStateMaximize - Maximized, wdWindowStateMinimize - Minimized, wdWindowStateNormal - Normal.

The wdWindowStateNormal constant indicates a window that's not maximized or minimized. The state of an inactive window cannot be set. Use the Activate method to activate a window prior to setting the window state.

Application.WindowState = wdWindowStateMaximize