I'm not sure if this is the right location for this type of question, but since I don't see a drools-specific forum and I do see drools posts in this forum, here goes...
I have what I think is a very simple rule to implement, but I can't find a way to do it without "cheating" by using an eval/function. Here's the basic rule in English:
Reject a claim if it contains a treatment that has already been claimed more than 70 times in the same calendar month.
rule when Treatment(id=="t1", status=="pending") Treatment(id=="t1", status=="paid") Treatment(id=="t1", status=="paid") then assert ( new Rejection("reason")); end