>I am actually doing this with Visual FoxPro 9, but I see that this function is not supported by Visual FoxPro 6. Do you happen to know what was the behavior with previous versions? Equivalent to sys(2340,0) (off) or sys(2340,1) (on)?

The SYS(2340) did not exists in VFP6 so there was no support for NT services, which would be

sys(2340,0)