Question about number locks

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My dad has an attache case (is that how it's spelled?) whose three-number combination he has forgotten. I'm trying to open it but I'm not good enough at math to figure out how many possible combinations a three-number lock has. I tried starting from 0-0-0 and went progressively up for starters. By which I mean, I went from 0-0-0 to 0-0-1, 0-0-2 and so on until I reached 9-9-9. If I'm counting right, I have already tried exactly 1,000 combinations. It still won't open. Before giving up and just breaking it open (the lock might just be busted after all), I would like to ask if anyone is aware how many possible combinations a three-number lock has. My brother said, "Use the factor nine formula," which I can't remember anyone but I think it was something like nine times eight times seven, etcetera, times one, then multiply the answer by three (I think? I've forgotten how he explained it). Does anyone else have an idea? My thumbs and forefingers hurt but I'd really like to not just destroy the lock if I can help it.