With the increasing dynamics in the economic and technological environment, the planning cycles in assembly planning are shortening. Especially for small and medium-sized enterprises (SMEs), assembly planning is a challenging task that could be very well supported by simulation. However, not least the lack of expert skills keeps SMEs from using simulation methods. The paper presents the development of a flexible simulation model for assembly planning, which the user can easily adapt using a spreadsheet program. The input data of the spreadsheets are processed by an algorithm, which allows the creation of various assembly system layouts. Additionally, the algorithm combines the layouts with their respective process logics. A case study shows that the presented approach not only enables the use of simulation without programming knowledge, but also has the potential to shorten and improve the assembly planning process.