Let's say, for common security measures, you want to display only the last four digits of an identification or Social Security number, credit card number, or other number and replace the rest of the digits with asterisks. Whether the digits in your cell are formatted as text, numbers, or the special Social Security number format, you can use the same functions. To display only the last four digits of identification numbers, use the CONCATENATE, RIGHT, and REPT functions.
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
Create a blank workbook or worksheet.
Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
In the worksheet, select cell A1, and press CTRL+V.
To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
Security Note: In the example, you should hide column B and protect the worksheet so that the original data cannot be viewed.