Previous research has identified several challenges that programmers face in answering questions about a code base. To explore ways to overcome those challenges, we have developed a prototypical programming tool called the Code Set tool. The tool allows programmers to work with sets of source code entities in novel ways, and this support allows programmers to more directly answer a range of questions about a code base. The main focus of this paper is on the design and implementation of the Code Set tool. We also report on a small user study that serves as a first step in evaluating the effectiveness of the Code Set tool.