Possible?

will this make you lucid program a computer to say "your dreaming" when your sleeping so you hear it in your dreams and become lucid?

There are mp3s like that out there, but from my own experiences with them, either they play too loudly for you to fall asleep, you fall asleep but don't hear them in your dreams, or you hear them in your dream and simply ignore the message. It's important to practice awareness and being mindful of your surroundings because relying on a message all by itself might not be as effective. :)

Yes, it will work, however it isn't such an effective method as one would think. I have had things like alarms, voices, and other things carry into my dream which would alert me that I am dreaming (though, of course, I would usually have to wake myself up for class or whatnot, much to my annoyance). However, when trying to simulate this, I have found you have to have the volume at the most precisely perfect level that it really isn't worth the effort. It either is too loud and wakes you up, or too quiet where you don't notice it. It is quite difficult to get that perfect volume. You can give it a shot, but as Puffin somewhat mentioned, it is important to practice the skills themselves than having to rely on external stimuli such as an audible message.

If you already don't become conscious of the fact that your dreaming by the wierdness of the dream, you may not even become lucid after hearing it in your dream. I personally haven't tried it however I would assume the volume would have to be perfect so that you won't wake up and you won't ignore it either.