I'm not certain, but I believe the issue is that custom ACE rules you define in the wizard are limited to the subset of SQL syntax supported by MSI; you can review the operators and keywords supported in this subset in the MSI Help Library page "SQL Syntax".
If you need more sophisticated checking, I gather you'll need to write a custom validator DLL, Ã la KB article Q108429 (
http://support.installshield.com/kb).
[P.S. I guessed wrong about the MSI syntax: ICE rules use MSI's SQL subset, ACE rules do not. See AllenSaxton's reply.]