2009 Ford Focus Keyless Entry?

I have a keyless entry remote from my last car 2004 Mercury Grand Marquis and I would like to make use of this remote on my 2009 Ford Focus. I have went through the programming mode several times and changed the battery. I'm able to reprogram my original remote for my for focus, but the other remote doesn't seem to want to program to my focus. I'm assuming the remotes are specific to each Ford. The remotes are physically identical… Am I at a loss here and have to order a extra remote for my focus or is there a way to use my old one?

Mercury remote will not work on the Focus. Different year, different car, different software.

You can't use remotes for different year production vehicles or different models in a specific model year. Don't buy after market remotes or you'll be starting a collection of remotes that don't work. Go to the dealer with the VIN and buy the correct remote.