I see no reason in your example calculation why the If calculation cannot be stored/indexed calculation--which is exactly what you need here for this "hardwired" calculation field.
I forgot that I could index a calculation field by unchecking "Do not store calculation results" under storage options. Thanks. By the way: Would you mind visiting another post of mine? I am still struggling on how to solve the problem: http://forums.filemaker.com/posts/dabaa30aa5