the author of this app says:
ZapBill is a program designed for use by doctors. The program allows you to input all of your billing information, and provides links to procedures and diagnoses. This allows you to categorize each office visit.
There is now a QuickPick list of commonly used codes and a modifier code list designed to modify codes more easily. There even has been an improvement in the ability to link with the datebook.
With this application, you simply need to input a patient's name and presto! Their patient history appears on your handheld!