Only opening one program at a time?

Question

I was wondering if there is a way to restrict a program so that only
one instance can be opened at a time.  I have two pieces of motion
control software that control the same piece of equiptment (one is for
maintenance and one is for normal operation).  I would like to
make sure that only one of the programs can be opened at a time. 
I thought of putting them into a single program with a tab structure,
but that suggests that you can switch between the tab, and I don't want
to allow that.  I also thought of having a pop-up when the program
first launches that askes which program you want to run, that way you
can only choose one or the other.   But you could still open
two instances of that application, one of each. 
The only thing I can think to do would be to use a global variable as a
flag and only allow the program to launch if the flag is off. 
However if the program crashed and didn't exit properly the global flag
would be left on and the program wouldn't start. 
Does anyone know if there is a good way to do this in LabView?
Thanks,
Kasey

Answer 1

You're welcome. I first used tabs in LV 6.1, before subpanels were available. I didn't want to run subVIs as popups, as a rule. The filetab was a good solution. The selected page obscures front-panel objects on the other pages, so each page is like a separate screen. I labeled the pages according to function, and the user could switch pages accordingly. Switching tab pages is easier than clicking a button on the main VI's front panel to pop up a VI enabling one function; then clicking "End" to disable; selecting another button on main VI's FP for another popup VI; etc.
But there were certain things I wanted to do without interruption (hardware interactions), so I disabled all pages but the active page as long as the critical task was ongoing. Also, I would disable certain controls even on the active page ("Start" button was disabled until the test was over, etc.). I don't think that strategy violates the spirit of the filetab.
The only trouble was that most of the pages had complicated functionality, so many of them had clusters full of option buttons. User would click one, I'd have to hide the option menu, show a bunch of other controls, etc. Straightforward but tedious. Subpanels make that kind of thing easier, because the VI running in the subpanel is responsible for its own front-panel display. And different people can develop different subpanel VIs at the same time, without too many problems merging.
Anyway, I'm glad your problem is solved. I just tried to run two instances of an LV 7 application under Windows 2000 and I couldn't. So that's good to know.
::Marty