Haven't tried. I expect you would run into trouble with the commas if you tried the whole thing at once like this:
Code:
 
rand(.25,.25,0,.25,.75,0,.75,.25.0,.75,.75,0)
You might think this would work:
Code:
 
(".25,.25,0",".25,.75,0",".75,.25.0",".75,.75,0")
But it won't--the parser I wrote doesn't care about quotes.

There may be a way though. Try this:
Code:
 
rand(.25,.75),rand(.25,.75),0
That ought to give you a randomly chosen quadrent. Remember to use center alignment in your style if you want the stimuli to be centered on these points.

For interested others: see Using Random Values in the guide for more detail on this function.

Hope that helps!
Blair