Scientific literature strongly indicates that IT business value is best observed on the level of business processes. However, methodologies by which the contribution of IT can be systematically analyzed on a business processes level are currently insufficient. Therefore, this paper presents a methodology which, proceeding from a given status quo, analyzes and measures changes in IT usage in business processes. The proposed methodology combines the possibilities of the methods Data Envelopment Analysis and Business Process Simulation. An example of application will demonstrate how effects on business process performance resulting from changes in IT usage can be analyzed and measured in a practical application by means of this methodology. The results show that this methodology bears potential for analyzing about the quantification of IT contribution to business value. It allows an assessment of IT business value due to changes in IT usage before an investment decision in IT is made.