Really, the best way to do this (if I understood you correctly) is just the start at the minimum possible number and increment up to the maximum.
Alternatively if what you want is for the computer to guess randomly, then you could use an array with as many elements as there are possible guessed, and "tick them off" like with a boolean, then refer to the corresponding array element when you generate a guess, and check whether it has already been guessed.
I didn't really understand what you were asking, so I could be on the wrong track.
