pick a number from 1 to 10

[rodchar]

Hi All,

I would like to have a web page where Internet users can go pick a number
from 1 to 10. However, once a user picks a number that number should not be
used again therefore that number belongs to that user.

How do I manage if, let's say, 2 users happen to pick the same number at the
very same time how do I prevent that from happening? Is that a concurrency
issue?

Thanks,
rodchar