>>>We talked about that before; I don't want to start this all over. This is not a surrogate PK but a user-specified.
>>
>>If your front-end check if the value is empty and make this textbox Readonly. You can do it also in When event assuming VFP application.
>
>Thank you but I don't like this approach; this will only raise questions that I don't want to answer.

So, how do you want to solve this problem? You can also make this textbox invisible in case of empty if that's what you meant by hiding.