Check out the paper published in the past in the SAS User's Group:
Cochran-Armitage Trend Test Using SAS
Hui Liu, Merck Research Labs, Merck & Co., Inc, Rahway, NJ
You can find it with a Google search for SAS FREQ TREND.
Also, example 29.7 of the FREQ procedure (available from SAS Help) will tell you how to do this. The example number could have changed in recent versions of SAS/STAT. But both FREQ and MULTTEST have good capabilities for this type of trend test.