In reply to Rick Wicklin.

thanks for the respose Rick!
I tried DO UNTIL loop at first place, but it took a very long time to run.
suppose I'm going to create a 5X10 multivariate matrix with range [0,100], I used the code below and it took SAS almost forever to run:

proc iml;
call randseed(123);
do until (X[,]>=0 & X[,]<=100);
X = RandNormal(1, mean, cov);
end;

Am I using the right code? would you please advice?
Thank you.