2002 Trailblazer LT Keyless entry remote

I am trying to program my remote that doesn't work. I replaced the battery and I tried the answer to an earlier thread ("key Less Entry remote #1 & #2") and when I turn the key on, off, on, off, while holding the unlock switch down, the horn blows and I release the switch. Then hold down both the lock and unlock button on the remote for over 30 seconds, but nothing happens. Finally after awhile the horn blew twice (i wasn't trying anymore) Is there any other method to doing this? :banghead: