I have a form that contains credit card numbers. I have set up a validation
block to hold those numbers, however, Ive run into a problem with Excel
simply changing the last digit. IE: 4000120078135436, becomes
4000120078135430. Ive tried setting the validation up thusly:

Allow whole number 0
Allow whole number 9
Allow whole number between 0, 9999999999999999
Allow whole number between 0, 99999999999999999
Allow whole number between 0, 0000000000000000
Allow Any Value, with the cell formatted to Custom, 0000000000000000

Nothing is keeping the number the way it was originally typed. If I set the
validation to text, it will alleviate the problem of the number being right,
however it will defeat the purpose of creating a cell to hold only numbers.
(BTW: the card number is bogus.)