A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
To clarify, this question has nothing to do with "lock a cell" -- In Excel that term has an explicit meaning.
What you're looking to do is express a cell reference as Absolute rather than Relative. In Mac Excel the keystroke for toggling through Relative/Absolute/Mixed references is Command+T, rather than F4. That as well as most other keyboard shortcuts are identified in Excel Help.
Also (although I suppose it may vary dependent on Regional/Language/Keyboard settings) the symbol used to represent absolute reference to a cell is $ rather than § -- just in case you decide to type it :-)