It happened in December when the stock market passed 13,000. It happened again in February when the Dow passed through 14,000. Now, as we bulldoze through 15,000 today we could be set for some sideways trading over the short term. Each time the Dow has broken through a psychological hurdle recently, we ended up trading in a volatile range over the next month. Atlantis Asset's Michael Cohn thinks the big number may be cause for a brief pause, but the Fed's spigot is what's driving this marktet - and it's not getting turned off anytime soon.