Multimedia elements addressing mathematical problems serve as an alternative or addition to classical forms of learning and teaching. Within the project math-kit we are developing a web-based toolbox to provide teachers and students with multimedia support to existing topics in maths. In this context, the integration of a computer algebra system (CAS) as a 'mathematical expert' offers many promising opportunities for the creation of internet-based learning units for undergraduate students. In this paper we show two examples of how the CAS MuPAD is used to create webbased mathematical drills with instant feedback.