1. A computer executable method for producing a computer model, operative to control a computer stored on at least one computer readable medium, the method when executed comprising: a) receiving a computer model formed of a plurality of variables from a first party; b) receiving a modification to at least one of the variables from a second party; c) determining whether the modification falls outside at least one predetermined criterion; d) if any of the modifications fall outside the at least one criteria, transmitting a message to the second party that the modification of the variable will likely result in the model producing an undesirable result.