In Australia there is a number formatting standard that requires thousands to be separated by a space instead of the " , " (comma). I had tried customising a number format that includes commas as the separators but never achieved what was necessary. Then a light bulb went on and I decided that the Windows Settings needed to be changed (Control Panel, Regional Settings, navigate to 'Digit Grouping Symbol' and replace the comma with a space). (See attached)
Then, back in MS Excel in Format Cells, choose to use a number format that has the option 'Use 1000 Separator ( )'. Note the space in the brackets.)
This has been great for most numbers but has a limitation. It will display correctly for two or three decimal places but does not display beyond that (e.g. 1 234 567.00 but 1 234 567.123456).