You will immediately die if you do them on the same day.
Just so you know, there is no distinction in the muscle between inner pec and out pec. The muscle fibers aren't laid out that way. You cannot make only one end of the fiber grow. The answer is to simply get larger pecs and typically the inner part will even out. But then again, pec shape is highly dependent on genetics.
All that said, yeah you can do them in the same day. Might help, might not.