No such thing,
Your chest works as two muscles, upper and lower, the fibres run from the sternum to the humerus. You can't work outer chest without working inner chest, but you can work upper or lower is that what you mean?
Anyway go to
www.ExRx.net and look at the muscle directory, you will see how the pecs work and it will tell you all the exercises you can do for upper and lower chest in the exercise directory.
HTH
SD