Chance of losing on Racetrax in MD, How is it calculated?

If a horse is racing 11 others and has a 20% chance of winning, what is the odds he will get in 1st, 2nd OR 3rd assuming his odds were true to begin with. In other words, what's the odds his bet for Show will pay off? I know calculating actual payout in this is a nightmare but is there an easy way to calculate what the odds are he will finish in any top 3 position?

I'm making this into a spreadsheet so if there is some easy functions in Google Docs that would help I can incorporate that as well. I just can't figure this part out.'

This is like the odds shown here:

Unanswerable.
How do they calculate chance of winning? Only a precise model of probability for any ranking (11! events) can answer the question. Your data don't provide this.