Infineon Villach wafer fab facility has a unique characteristic of producing products of different wafer sizes with shared resources, both operators and tools. Daily adaptation of resource allocation to manage changing workloads is done dynamically and imposes challenges in providing high accuracy simulation forecast. In this paper, we discuss the modelling approach that we have taken to represent this dynamic feature, where resources are adjusted in simulation based on WIP situation. The concept is similar to acquiring KANBAN prior to running a production lot. KANBAN quantity is kept at a minimum number in low WIP situation, while the quantity is kept at maximum number at high WIP situation. These values were adjusted by studying the historical moves observed for a period of 3 months. Using this approach, we managed to improve the forecast quality by 7 percentage points in moves and 64 percentage points in WIP.