This paper explores the importance of integrating knowledge with quantitative modeling process to improve sales operations in multiple product selling situations in the pharmaceutical industry. A knowledge-based approach is proposed to minimize challenges in detailing multiple products to physicians who are more and more difficult accessing in recent years. The performance of this new approach is compared against the traditional approach via actual implementation by the firm that is sponsoring the research. Results based on three months of implementation indicate that the knowledge-based approach performs significantly better with increasing the number of responsive physicians by 71% and profit by 9%.