Abstract: A system for building interactive calculations on web pages, comprising a central processor for executing program instructions stored on computer readable media, interfaces in communication with the central processor, one or more computer readable media in communication with the central processor containing program instructions for executing a manager object for controlling the interaction of objects, one or more than one calculation objects (26, 28) in communication with the manager object, one or more than one input objects (14, 16, 18) controlling the model parameters, one or more than one output objects (20, 22, 24) displaying values of calculated variables, wherein the manager object, each of the input objects, and each of the output objects are coded with no model specific information, and model specific information is communicated through the manager object by parameter or variable name.