Ian,

RLOCK() and FLOCK() both will attempt to lock a record or file and if they succeed the functions return .T. Your code;

IF RLOCK() = .T.

is locking the record (BTW, you don't need the = .t. at all).

If you want to know if the rlock failed (because someone else has it locked then use code like this;

IF NOT RLOCK()
   Wait window "Somebody else is working on this record
ELSE
   UNLOCK
ENDIF