>Hi Kamil,
>I've taken the hang problem into consideration.
>In my idea, if the computer hangs, the locked record will allow edit again in 3 ways:
>1) allow the same user to re-login to edit the locked record
> again regarding the locking flag.
>2) allow any other user to edit the locked record if it
> has been locked for over a period, such as over 3 hours.
>3) add function to unlock the record manually.
>to do above function, I need three more fields to record
>the locking status: locked, locked_by, locked_at
>
>Do you have any other comment?

Hi Samuel.
I think Michel's idea is a good one.
However i prefer to use as little amount of field space as possible. In view of this i would use only one DateTime field and a timer on the editing form. I did not test this consept though, so i am not 100% confident.
Best wishes.
Kamil