The LEGO educational programming environment, called "RoboLab", is a known programming environment for children, aiming to teach basic programming skills. LEGO has already performed numerous evaluations concerning various usability aspects, aimed to enhance the overall usability and utility of the product. This study focuses on a more academic parameter, namely the combination of different usability evaluation methods on the same educational software, as well as on the combination of their results. So, two expert-based methods have been applied, a Cognitive Graphical Walkthrough and a Heuristic Evaluation. The results of the study unveiled some problems and shortcommings of the interface as well as some limitations of the employed methods.