Use the Reference dialog box to select the topics and topic item from which to build the computed item definition.
The Reference dialog box is split between topics in the left pane and topic items in the right pane. The topics displayed in the left pane are derived from the topics in the Request pane. The items displayed in the right pane are the values which make up each topic. Before you can select a topic to use in a computed item expression, you must select it and a topic item.