If you plan to do an APPEND BLANK and an RLOCK, then I think you should turn buffering off; it just doesn't make sense in the current context.

Even then, someone else could lock your appended record before you get a chance to lock it.

What I do is (with MULTILOCKS ON):

IF RLOCK( "0", ALIAS() )        && Lock Header
   APPEND BLANK
   IF RLOCK()
      UNLOCK RECORD 0       && Unlock Header
      ...
   ELSE
      UNLOCK RECORD 0       && Unlock Header
      ...
   ENDIF
ELSE
   ...
ENDIF
UNLOCK ALL

>I do an APPEND BLANK then a RLOCK(). The reason for locking is that the newly appended record often appears in other users sessions even before it is TABLEUPDATEd.