How to avoid mutiuser edit the same record in Edit Form

[Cheng-Liang Shen]

Hi

How can I lock the record once I open Edit Form to edit the record? I
already set the pessimistic on the form but the problem
I meet is when first user open the Edit Form but before he does any edit
record action, other user can still edit the record. Therefore,
I wonder how can I lock the record once the Edit Form is open. Thanks.