Hi Yh Yau,

First, create a field named Editing, or whatever you want, of type tinyint or smallint, set the default value to 0 (zero)

Second, before beging the edition of the record, update that field with 1,
you can use sqlexe command to do that,
when you finished editing, update the field with 0 to set it "Editable" again

Of course, you have to reprogram the form to check if that field is set to 0 or 1 before beging editing,

that fiels is like a Switche on/off

Regards
Amilcar Pino