I don't recommend using a program like that, because you can easily cheat the players. You should try doing what dice sites do, and have a server seed and a client seed, with the client seed being chosen by the participants. (Ex: Everyone picks 4 numbers, and they are joined together. Try reading the info on Primedice's probably fair system, as it is basically my suggestion.
I agree with you, It sounds like it can be easily manipulated.