Returns or sets the vertical split percentage for the specified window. Read/write Long.
expression.SplitVertical
expression Required. An expression that returns a Window object.
To remove the split, set this property to zero (0) or set the Split property to False.
This example splits the active window so that the top pane occupies 70 percent of the window.
ActiveDocument.ActiveWindow.SplitVertical = 70
This example splits the window for Document1 in half vertically.
Windows("Document1").SplitVertical = 50