If you are using a DBC, AND the DBC is not already open, you can open it exclusively by issuing

ON ERROR QUIT && if the DBC can not be opened EXCL, someone else is running EXE
OPEN MYDBC EXCL
ON ERROR DO_YOUR_ERROR_PROG



>I have execute file call ac.exe, I want to make this exe only single user can use . How to make exe to single user environment . In login form ie ok button and cancel button. In ok button, I do set the public
>variable multi_user to "N" as belows:-
>
>Multi_user = "N"
>then In the Ok Button check :-
> If Multi_user ="N"
> set exclusive on
> else
> set exclusive off
> endi
>
>I test run, Two persons still can get in
>then i try the other ways. I put same code into the Main.prg, Well I works. It come out the message : Access Denied. But the problem the message box have three buttons ie cancel, ignore, help. I try to click ignore... It let me into the program.... Why