How long does it take for my pecs/chest muscle to grow?

Hi, I just turned 14 and i'm about 5'8. Every night I drink milk with this medicine that supports my health/muscle and immune system. Before I workout I stretch/play basketball for warm ups then I get to my workout. I found this video on youtube which is suppose to grow my muscle. http://www.youtube.com/watch?v=jWc8gHlAkoM (Im on that one because the level 2 of it is too hard for me to complete and I dont want to over train myself.) Also, after my workout I drink this thing that's called "Muscle milk". I want to know how long would it take me to get a good chest muscle. Thanks in advance.