Much computerized support for knowledge workers has consisted of tools to handle low-level functions such as distribution, storage, and retrieval of information. However, the higher level processes of making decisions and taking actions with respect to this information have not been supported to the same degree. This paper describes the ISCREEN prototype system for screening text messages. ISCREEN includes a high-level interface for users to define rules, a component that screens text messages, and a conflict detection component that examines rules for inconsistencies. An explanation component uses text generation to answer user queries about past or potential system actions based on Grice's conversational maxims.