I know the example that I gave was not that good. Say that it's a 5 digit number and I need to validate the 5th digit, that is when multiple the 2nd and fourth digit by 2 and add the results to the 1st and 3rd digit you take the total of the answer and if the last digit in the answer matches the 5th digit, it validates true, else false.
I hope this clears it up. I know there is an easier answer, I just can't figure it out. Maybe I am thinking to hard on it.
Thanks
John