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     It seems to me that what you need is just to use some custom evaluators. For instance, you could implement an "inRange" evaluator that takes a range an matches when the given value is included in the range. Example:

MyFact( myValue inRange "428.0-428.9" )

     Behind the scenes, you are still calling a method that is doing the range matching verification (not much different than calling the method in an eval block), but this has several advantages over the use of eval, starting by the simplicity on rules authoring, improved testability and *specially* the ability to improve node sharing among rules. Developing custom evaluators for Drools requires a developer to write a class that contains some boiler plate code, but even someone that never implemented one before should be able to develop and test the operator in less than a day. After it is done, you can simply start using it everywhere.