The ISNA Function is to check whether a value is #N/A error.
Formula:
=ISNA(value)
Explanations:
Value is required, the result returns TRUE when the value is #N/A error, and returns False when it is not.
Example:
=ISNA(A2)
Cell A2 is Text, not #N/A error, so ISNA(A2) returns False.
=ISNA(A3)
Cell A3 is #N/A error, so ISNA(A3) returns True.