LOCK

The LOCK(<filename>) function is similar to the MOD(<filename>) function. LOCK(...) will return -1 if the current record in the specified file has been successfully locked by the user or program, or 0 otherwise.

Note: LOCK(...) does not test whether the record is locked by any other user or in any other MDI window (just as MOD(...) doesn't test whether the record has been modified by any other user or in any other MDI window).