This paper reports on our industry-academia project of using a functional language in business software production. The general motivation behind the project is our ultimate goal of adopting an ML-style higher-order typed functional language in a wide range of ordinary software development in industry. To probe the feasibility and identify various practical problems and needs, we have conducted a 15 month pilot project for developing an enterprise resource planning (ERP) system in SML#. The project has successfully completed as we have planned, demonstrating the feasibility of SML#. In particular, seamless integration of SQL and direct C language interface are shown to be useful in reliable and efficient development of a data intensive business application. During the program development, we have found several useful functional programming patterns and a number of possible extensions of an ML-style language with records. This paper reports on the project details and the lessons learned from the project.