Workload control (WLC) is a production planning and control (PPC) concept specifically designed for complex manufacturing environments, with particular relevance to the make-to-order (MTO) sector and small and medium sized enterprises (SMEs). Its main principle is to keep the length of queues on the shop floor at appropriate levels to meet the promised deliver dates, taking into account the system capacity and capabilities. If these queues are kept short and stable, then waiting times and therefore flow times will be firmly controlled and reliable. It is possible to identify three hierarchical levels, related with stages in the order flow, at which the control of these queues can be attempted, namely order entry, order release and priority dispatching (Breithaupt et al., 2002). At each level, a decision must be made relatively to the orders allowed to proceed to the next stage and whether this requires capacity adjustments.