Limit input Choices based on value in another database

I would like to select from a restricted list of values populated by querying another DB.

For example, entries into Field A in DB AA would be limited to the values in Field B in DB BB where Field C in DB BB is equal to some value. I’ve tried to put various lookup functions into the choices and/or formula properties box without success. Thanks.

Sorry, what you are asking for is not possible.