In reply to David Mangen.

Yes. If you are using an old version of SAS, you can replace the call to the RANDFUN function by
car = j(NumSim,1);
call randgen(car, "Table", {1 1 1}/3);
By the way, there have been five releases of SAS/IML since the 9.2 days, so there are a LOT of new functions!