In reply to bill.

If you have 18 or fewer points, you can use the ALLPERM function to generate all permutations and do exact tests. Otherwise, you'll have to use the RANPERM function to generate lots of random permutations and approximate the sampling distribution. Both of these functions are discussed in the article "Generate permutations in SAS." In case you wonder why 18 is the cutoff value, see "On the number of permutations supported in SAS software."