E-commerce applications automate various business processes within an organization. To maintain a competitive edge, business analysts frequently modify business processes. Determining the effort for modifying a business process is not a trivial task, since the changes to the business process will result in changes to the source code for which the business analyst has limited knowledge. In this paper, we propose an approach for tracing the propagation of a change from the business process level to the code. We derive a change impact metric which estimates the code to be modified as a result of a business process change. A case study, using a large e-commerce application from the OFBiz open source project, demonstrates the effectiveness of our proposed change impact metric.