1. A simulation system for use in simulating the operation of a portion of a process plant, the simulation system comprising: one or more simulation blocks configured to perform simulation of one or more pieces of equipment within the process plant, each simulation block including; a process model that models a portion of the process plant; a simulation unit that uses the process model to simulate the operation of the portion of the process plant to produce a simulated output for a process element associated with the portion of the process plant; an input adapted to accept an indication of an actual value of the process element corresponding to the simulated output for the process element; and a model regeneration unit that compares the indication of the actual value of the process element with the simulated output of the process element to develop an updated process model for use by the simulation routine.