Trap and handle #N/A errors
Return value 
The value supplied for #N/A errors
value - The value, reference, or formula to check for an error.
value_if_na - The value to return if #N/A error is found.
=IFNA(value, value_if_na)

The IFNA function can be used to trap #N/A errors that may occur with the VLOOKUP function. In the example shown, the formula in F5, copied down, is:

=IFNA(VLOOKUP(E5,xtable,2,0),"Not found")
where xtable is the named range B5:C12. When the lookup value in column E is found in xtable, VLOOKUP returns the exchange range normally. When the lookup value is not found, VLOOKUP returns #N/A, and IFNA catches this error and returns "Not found".