A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Ctrl+Tab is the OS X keyboard shortcut for switching between currently running programs.
To switch between open windows of the same program Ctrl+` is the appropriate keystroke.
Check again Bob,
Unless your Computer is set different The "Application Switcher" shortcut is Command - Tab (⌘ - Tab)
Or if you haven't set Keyboard so that Function Keys (Fn) has been switched to activate certain apple System actions (reverse of what it is Normally) it may be
Fn Command - Tab (Fn - ⌘ - Tab)
Follow Annotation Directions in screenshot
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