This research presents a methodology to develop a computer system "CSC-Estimate", Computer System for Construction Estimates, that stresses on the early and preliminary stages of estimating the construction costs of any commercial building that also can be used for residential buildings if a reduction factor of 20 to 30 percent is considered. The methodology utilizes tools available between hands, Access 97 the database member of Microsoft Office 97 family and Visual Basic for Application, the child of the Object Oriented Programming Language Visual Basic (6.0). The methodology introduces a new tool to be used for the construction industry in general and for the Canadian industry in particular. "CSC-Estimate" is designed to generate parametric and preliminary estimates to be used by the owner for feasibility purposes, by the architects and engineers for conceptual estimates or when considering alternatives, as well by the contractor for bidding purposes. Two cases consist of actual projects are presented in order to illustrate the effectiveness and performance of the proposed model.