CVS Facebook offer: Like them, print 20% off shopping pass... limited quantities

If you Like CVS on Facebook, you can enter your CVS Extra Care number and email in to have a coupon for  20% off your order emailed to you.  I was able to claim mine this morning and my coupon expires 12/5.  The 20% off excludes sale items.  Their status said it is limited quantities, so I have no idea when this offer will end.