Gets or sets the active windows to which some sheet and workbook options like zoom will apply. (1 based) Note that spreadsheets normally have a single Window, so this value will most likely be 1 and should stay that way. If you are working with multiple spreadsheet windows, you can change this property to change the sheet options of a particular window. The properties that apply to a specific window and are affected by this property mention it on their docs.
property TExcelFile.ActiveWindow: Integer