I am wanting to validate numbers as they are keyed in against a list of valid numbers. For example, I will have a list of 1000 - 9 digit numbers, and I would like to check a number as it is entered against that list. Furthermore, I would like a valid number, once entered to no longer be valid, or only be allowed to be entered once

For instance, my valid numbers list is 800000001-800000999 and when 800000235 is eneterd it is determined to be valid, however I do not want that exact number to be allowed again

I imagaine that this can be done in either Excel or Access and I am fine with using either

Any help would be greatly-greatly appreciated

Thanks

dcs