This paper proposes a real-time production planning and control method for multiple products to be produced on a single facility with machine changeover costs. This technique, called the DBL method, considers not only the current inventory levels of input items but also forecasted supply quantities, thereby enabling the maintenance of production cycles. The use of this technique allows real-time determination of which input items should be produced and in what quantities whenever the facility becomes idle. Results from various experimental designs using BLOCS, an object-oriented application program, are also presented.