How to randomly select variables in SAS?

I can find all sorts of information on how to randomly select observations in SAS which is a fairly easy task. This is not what I need though. I need to randomly select variables. What I want to do specifically is randomly choose 20 variables from my list of 159 variables and do this 50 times. I want to ensure diversity too. I have been spending about two days on this and am having no luck.