add some javadoc to warn that stale cached formula cell values may result in incorrect evaluations, and what to do about it (evaluate formula cells before asking the rule if it applies). Doing it for the user turns out to not be that easy, as the FormulaEvaluator instance in use is not known in this context.
poi/trunk/src/java/org/apache/poi/ss/formula/ConditionalFormattingEvaluator.java