Implementation of known O.R. models has faced a number of hurdles. In this paper, L.P. models have been developed for combined Production-Marketing System of a manufacturing company. The product is a wristwatch of different types. First a yearly model is developed for multi-periods. Next an updation model is developed based on the performance of the previous quarter. If the performance is not up to the expectation, then another L.P. model is developed to minimize the deviation. The solution is implemented as a Decision Support System (DSS) and tested for a year.