The document presents a guideline for an alternative approach to classic interregional computable general equilibrium (IRCGE) modelling, suitable for studying the impact of policy reforms at a local sub-national scale. First, the author describes a method to produce operational data which can be used in an IRCGE model. Then, a classic implementation is presented on the basis of these data with some simulation results. After having shown the limitations of this approach, he provides the reader with the main features that should guide the alternative model, and show how the results could be profitably interpreted in the framework of spatial economics theories.