Reverses the value of its argument. Use NOT when you want to make sure a value is not equal to one particular value.
Logical is a value or expression that can be evaluated to TRUE or FALSE.
If logical is FALSE, NOT returns TRUE; if logical is TRUE, NOT returns FALSE.
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.