Hi, dandigger;
Two quick thoughts:

1) If all you want is an alert: Conditional formatting using a formula like:
=countif($A:$A,$C1)1
Then format patterns yellow, all entered into the county results column.
Where
Column A: zip codes in your lookup table
Column C: zip codes entered to perform the lookup.

2) For a more complete solution: Multiple county columns in both your lookup
table and your results area, i.e.: county 1, county 2, as many as necessary.

Regards,
Ian.

"dandigger" wrote:

I've created a vlookup to pull state and county when a zip code is entered.
Problem is that some zip codes are in multiple counties. for example: I live
in 54115, which is in Brown and Outagamie counties. the lookup only returns
Brown as it is listed first alphabetically (I assume). Any formula I can add
to let the user know of error or that multiple options/counties are
available? Thanks again