This function, Is Not Available, tests whether a value, an expression, or contents of a referenced cell has the not available (#N/A) error value.
ISNA(cellreference)
ISNA(value)
ISNA(expression)
Specify a cell reference, a numeric or text value, or an expression for the argument.
Use this function to test the contents of a cell, a numeric or text value directly, or a function or expression.
This function returns TRUE if the value is or refers to the Not Available error value, and returns FALSE if the value is or refers to a cell with no data.
Accepts any data type for an argument. Returns Boolean (TRUE or FALSE) data.
ISNA(B12)
ISNA(R12C2)
ISNA(#N/A) gives the result TRUE
ISNA(NA()) gives the result TRUE
ISNA(#REF) gives the result FALSE