Utilising dynamic simulation methods to estimate manufacturing resources, can improve unit cost estimation and aid design decisions. This paper introduces a framework specification that combines Computer Aided Design (CAD), Computer Aided Process Planning (CAPP) and Discrete Event Simulation (DES) technologies. The framework is used to aid a design team in understanding the consequences of design decisions in terms of cost and manufacturing resources, by returning unit cost and manufacturing based results, directly to the design team, within the design environment. Dynamic Resource Estimation System (DRES) is a system being developed to implement the framework and is presented in this paper.