1. A system for building interactive calculations on web pages, comprising: a central processor for executing program instructions stored on one or more than one computer readable medium; a first user interface in communication with the central processor; a second user interface in communication with the central processor; a first computer readable medium in communication with the central processor containing program instructions for executing a manager object for controlling the interaction of objects; a second computer readable medium in communication with the central processor containing program instructions for executing one or more than one calculation objects ( 26 , 28 ) in communication with the manager object on the first computer readable medium; a third computer readable medium in communication with the central processor containing program instructions for executing one or more than one input objects ( 14 , 16 , 18 ) controlling the model parameters, in communication with the manager object on the first computer readable medium and the first user interface; a fourth computer readable medium in communication with the central processor containing program instructions for executing one or more than one output objects ( 20 , 22 , 24 ) displaying values of calculated variables, in communication with the manager object on the first computer readable medium and the second user interface; 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.