1. A method of controlling application usage in a plurality of computers, the method comprising the computer-implemented steps of: evaluating an application program operation on a first computer, wherein the evaluating step evaluates at least one rule pertaining to the application program operation, wherein the at least one rule is among a plurality of rules stored on the first computer, and wherein the at least one rule contains at least one expression used by the evaluating step to control application program operation; communicating with a second computer as indicated by the at least one rule; and confirming on the first computer that the second computer has an ability to interact with the evaluating step.