There are several computer aided design systems which exist to aid the conceptual phase of design. These CAD systems provide adequate geometry input, but often lack the capability to interactively obtain large amounts of numerical and text input often needed by analysis software. An interactive method for facilitating this non-geometric input to conceptual design analysis systems is needed. This thesis describes the creation of a spreadsheet input system to fulfill this need. The requirements, functional specification, and design of the system are addressed using a software engineering methodology. Accepted standards for programming and graphics, namely C and PHIGS, are used in the implementation. This is a system which can be used either to enhance existing CAD software or in the creation of new CAD systems. The use of this spreadsheet system in the enhancement of the well-known aircraft conceptual design system ACSYNT is also described in this thesis. / Master of Science