You can not. Trades must be reported in the year executed.
You probably should amend
How to Amend (Change or Correct) a Return You Already Filed
http://turbotax.intuit.com/support/iq/Amend-a-Return/How-to-Amend--Change-or-Correct--a-Return-You-A...
You can always not amend of course. If the IRS never picks up on the "missing" 1099-B then you simply lose the deduction you're entitled to from a security loss. If the IRS does pick up on the missing 1099-B then you can either agree to pay the tax, (if the basis isn't reported they'll tax you on the proceeds), or amend at that time.
Tom Young
