Check Value exists

Hi all,

I am trying write a calculation based on where a value exists - have tried isempty, exists etc. 

CASE
WHEN
    IsEmpty([Reason Code].[Reason Code].&[3]) 
THEN "EMPTY"
ELSE
    "Not Empty"
END

The above returns "Not Empty", eventhough the value does not exist.

Have tried Exists() - but that just a "#VALUE!" error

Thanks in advance!

Keith.