Custom Field with Unique Values Only

[theun4gven]

Is there a way to have a custom field, or even a standard field for that matter, only contain unique values? Each of my DVDs is stored in a sleeve and has a unique value. I have noticed that from time to time when I enter the values into the my custom ID field, I have mistyped a number and ended up with two entries each having the same ID. Is there a way to have the program warn me when I have entered a number that already exists?

Thanks for any help you can provide?

[Conor]

There is no enforcing of a unique id in any of the current fields, this gives all the fields the greatest possibility. Thank you for the feedback, will keep it mind when adding new custom fields that one with a enforced uniqueness would be useful.