In order to help the knowledge engineer during knowledge modelling phase, we developed an environment for the conceptual modelling language CML offered by the CommonKADS methodology. This environment, called Cokace, was designed using Centaur, a programming environment generator, that was usually exploited for building environments dedicated to software engineering languages. Thanks to Centaur, Cokace provides the knowledge engineer with structured edition, static validation and dynamic interpretation of CML expertise models. Cokace allows the knowledge engineer to simulate a reasoning on CML expertise models, and enables verification and evaluation of such expertise models before implementation of the final knowledge-based system. This work illustrates an example of the benefits knowledge engineering can get from well established techniques and tools available in software engineering.