=IF( CountIf(a1:a10,"Joe")<1, CountIf(a1:a10,"Joe"),
LookUp(..etc...) )

will give you the count if there are more or fewer than one.
Otherwise, it performs the lookup.

- David

On Jul 23, 9:12 pm, bonot1 wrote:
I am using LOOKUP functions to retrieve info from a list. Some of the lookup
values have more than one match in the list. Is there a function that allows
me to retrieve multiple elements for one lookup value, or at least a function
that tells me there are duplicate matches?