PdaGraph is an end-user component-based programming language for the PDA. In the first stage of our research a data-flow visual programming language was designed, but this was lacking an intuitive user interface and the connections between different parts of the program were not visible. To make PdaGraph suitable for end-users, we designed a high-level component-based message-flow programming language and environment. To verify that the design is end-user friendly we conducted a usability study using a low fidelity paper prototype, and feedback was obtained by videotaping the subject-system interactions and by using a cognitive dimensions questionnaire.