Int 7F Fn 41  - Alloy Ntnx - Lock File For User                            [N]

   AH = 41h
   AL = user ID
   DS:DX -> ASCIZ filename

Return: AL = status
       00h successful
       01h invalid function
       02h already locked
       03h unable to lock
       04h lock table full

Note:  requests exclusive read/write access to file

See Also: AH=00h,AH=41h"MW386",AH=42h"NTNX"