If a built-in number format does not meet your needs, you can create a new number format that is based on an existing number format and add it to the list of custom number formats. For example, if you're creating a spreadsheet that contains customer information, you can create a number format for telephone numbers. You can apply the custom number format to a string of numbers in a cell to format them as a telephone number.
Custom number formats affect only the way a number is displayed and do not affect the underlying value of the number. Custom number formats are stored in the active workbook and are not available to new workbooks that you open. For more information about changing the settings for new workbooks, see
Control how workbooks and sheets are created.
Do any of the following:
Create a custom number format
Apply a custom number format
Delete a custom number format