In today's technic alworld (e.g., in the automotive industry), more and more purely mechanical components get replaced by electro-mechanical ones. Thus the size and complexity of embedded systems steadily increases. To cope with this development, comfortable software engineering tools are being developed that allow a more functionality-oriented development of applications. This paper demonstrates how worst-case execution time (WCET) analysis is integrated into such a high-level application design and simulation tool {Matlab /Simulink} thus providing a higher-level interface to WCET analysis. The Matlab /Simulink extensions compute and display worst-case timing data for all blocksof a Matlab /Simulink simulation, which gives the developer of an application valuable feedback about the correct timing of the application being developed. The solution facilitates a fully-automated WCET analysis, i.e., in contrast to existing approaches the programmer does not have to provide path information.