The other method that is used, but its essentially for playing the exotics is to create a simple Monte Carlo simultaion program in excel say using 5,000 simulations
9depending on the speed of your machine) then run 4 or 5 tests and record the results for each test run, so you get the Probabilities for each runner to fill all placings this is a far better alternative than using the Harville formula which distorts probabilities somewhat.