Each year I bet my student class that two students will share a birthday. Nice to see this example worked through using something very much like a Monte Carlo simulation! Of course, it would be fun, if possible, to add parameters such as the probability distribution for the initial assignment of 'birthdays' to each member of the room (birthdays neither have a uniform (flat) nor normal distribution, but depend on the seasons, vacation times, and even power outages and major televised sports events!). This would then be a VERY useful example of Monte Carlo simulation. But like zonkerz hinted in another review, a 'stop' button would be useful to avoid force-quit when setting the number of trials too high for whichever machine you're running on! Nice job! Thanks!