>Note that if User A save it changes before User B change a field, there will not be an error. Also, the edit button doesn't do anything. Maybe you should try to lock the record yourself in the Edit button.

I found the problem. I wase using TableUpdate(.F.). The online help says:
If nRows is 2, changes made to the table or cursor are committed in the same manner as when nRows is 1. However, an error doesn't occur when a change cannot be committed.

Changing to TableUpdate(.T) solved the problem. Thanks soo much for the help.

I am however concerned that if user A updates the changes before user B changes a field, no error will occur. In this case user B will have no idea that the record he is changing has already been changed by someone else.

Does anyone have a way to deal with this?