A user is prompted for a 2 character code on a userform.
If the the code exists, the user is prompted for a differnent code.
The challenge is that AA is valid if Aa exists.

Using Exact and a Vlookup will not work given the vlookup returns the
first value it finds. this only works in the case where AA exists but
not aa. but when AA and aa are both in the list it no longer works.

thanks, ideally i'm looking for a vba solution.

Acceptable List
AA
Aa
aa
aA
BB

Unacceptable List
AA
AA
AA