Ant.
Go to
www.propokertools.comthey have a calculator which is good, but theen you should download odds oracle as its the nuts!
the system they use to calculate this is they take each hand, run XXXXXXXXboards out and record the results, theese calculators are capable of doing millions of simulations in a minute or two.
Also, like Andy says, there is no way you can say preflop, he's defo folded an ace unless you have ridic hero reads, so really dont worry about it