I need to do a validation on a subset of a list. My data is as follows

In A1 is the Value "AL"
in B1 i would like to validate based on the below data in A5:B9, but i only
want the values for state AL - Autauga and Baldwin to show in the Validation.

State County
AK YAKUTAT BOROUGH
AK YUKON-KOYUKUK
AL AUTAUGA
AL BALDWIN