I have not seen storage lockers in any airport for a good long time. Some large international airports have left luggage services, where they have facilities to screen the checked luggage for contraband before accepting them.
I just looked at the Charlotte Airport website and see they have a business center. They say to call for more info. I'd suggest you do just that: Call their business center and ask about storing a package for a day.
http://charmeck.org/city/charlotte/A...essCenter.aspx