The complex interactions of natural swarms, for example formed by some social insects, are difficult to comprehend. Considering tasks such as nest-building, the necessary underlying communication presumably happens indirectly by changing and reacting on the environment. This paper presents an overall approach to interactively evolve rule-based swarms that create three-dimensional structures in continuous space. The approach comprises the design of the swarm agent, details about the breeding process and first results. A swarm is determined by a set of flocking parameters and a set of instructional rules that allow the agents to change their local structural environment. The center or focus of the swarm's endeavour may be shifted either on a swarm agent or on a fixed point in space. The alteration of the supplied 3D structure during the course of evolution enables an external supervisor to interactively guide the development of a swarm.