Here's what I've done, and it doesn't work, so I'm obviously not doing what you're suggesting -
Column 1-
Field: PositionID
Criteria: LCase([Enter Y or N])
Column 2
Field: PositionID
Criteria: (In (3,5,7,9) And "Y")
Or: (In (2,4,6,8) And "N")
The error message is - This expression is typed...