'COUNTIF' Function is not preventing '#N/A'

[carlosbourn]

I am using the following COUNTIF formula which I am sure is supposed to prevent '#N/A' from appearing (According to http://www.ozgrid.com/Excel/stop-na-vlookup.htm)

=IF(COUNTIF(B10,PORT),"",INDEX(Ports!$A$3:$BD$54,MATCH(Jun08!C10,PORT,0),MATCH(Jun08!D10,Ports!$A$2:$BD$2,1)))

However, #N/A is still appearing in the worksheet when no data has been input.

As this is something we are going to be presenting to a client, I am keen to ensure it doesn't contain #N/A all over it!

Thanks in anticipation