Thanks for your help :)
well VI, i need only number codes in fact.

I was thinking of another problem :P, what if after a couple of year i've generated tons of Pins, wha should i do?? reset them all? (i don't think this is a good idea, cause people might use their old pins), maybe adding one more digit?? (adding a digit is a pain in the ass for users, but all new pins would be unique)