The ability of parametric computer-aided design systems to generate models rapidly enables designers to explore the downstream impacts of changes to key design parameters. However, the typical modeling functions provided in the parametric systems can become insufficient when such exploration is needed for increasingly complex parametric design models. Main challenges for exploration that we observed are control and analysis of changes on the design model and in particular, when they are introduced continuously. The system interfaces and the human-visual perception system alleviate these challenges. In this study, we demonstrate ViSA, a Visual Sensitivity Analysis method that aims to make the effects of change within a parametric model controllable, measurable and apparent for designers. The approach aims to improve visually analyzing the sensitivity of a design model to planned parametric changes. The method proposes customizable control and visualization features in the model that are decoupled from each other at the design level, while providing interfaces between them through parametric associations. We present findings from our case studies in addition to the results of a user study demonstrating the applicability and limitations of the proposed method.