Thanks Gripphon, very clear and very precise. You also made me realise that I had the wrong calculation about Trav drop in my previous post. I agree, the chance to drop at least one of Ber/Jah/Cham should be: Code: 1 - (1 - Ber) * (1 - Jah) * (1 - Cham) It should not be the simple "Ber + Jah + Cham" as they are not independent events (this is the factor I forgot to consider, as I simply thought they are mutually exclusive ...). Theoretically, you could get a Ber and a Jah from a single member, is it right? I will correct my previous post. Cheers.