The Excel #N/A error is produced when a value is not available to your formula.
The Excel ISNA function tests if an initial supplied expression (or value) returns the Excel #N/A Error, and if so, returns TRUE; Otherwise the function returns FALSE.
The format of the function is :
Where the value argument is the expression or value to be tested. This can be either supplied directly to the function, or can be the name or reference of a cell containing a value or formula.
The following spreadsheet shows several examples of the Excel Isna function.
The above examples use different argument types, including:
Note also that, in the above examples:
Further information and examples of the Excel 'Is' functions can be found on the Microsoft Office website.