Thank you Sergey,
I appreciated your help again. Allow me to use this reply to ask you very simple for you question. In our app I am trying to lock all tables so we can do the process that requires exclusive access to those tables. Now, users can use those tables exclusive already at that moment. I opened FoxPro in another session to simulate another workstation and used a couple of the tables exclusive. In the script I am checking if those tables are used.

IF !USED(lcFileToLock)
  USE (lcFileToLock) IN 0
ENDIF

The condition is TRUE and program execution goes to USE() statement and then the error is generated "File access denied". How could I check if tables I am trying to lock are used already so I will not try to USE() them again?
I looked the Help up but can't (or not able) to find what should I do.
Regards
Igor