It has nothing to do with using or not using buffering. It's about primary/candidate keys and proper error trapping applied on INSERT/REPLACE or, in case of buffering, TABLEUPDATE().

>Between the time you search for the key and then write the key, another user *can* have written the key in the intervening time.
>
>>Why will it fail in multi-user environment?
>
>>>If yo don't want to use buffering (IMO it would behoove you to spend the learning about it as soon as possible) then you could use an unbound textbox control so you have a change to look up the key.
>>>
>>>Be aware, though, this will fail in multi-user environments.
>>>