Module cohesion describ es the degree to which different actions performed by a module contribute towards a unified function. High module cohesion is a desirable property of a program. The program modifications during successive maintenance interventions can have negative effect on the structure of the program resulting in less cohesive modules. Therefore, metrics that measure module cohesion are important for software restructuring during maintenance. The existing static slice based module cohesionmetrics significantly over estimate cohesion due to the limitations of static slicing. In this paper, we present a novel program execution based approach to measure module cohesion of legacy software. We define cohesion metrics base down definition-use pairs in the dynamic slices of the outputs. Our approach significantly improves the accuracy of cohesion measurement. We implemented our technique and measured module cohesion for several programs. Cohesion measurements using our technique were found to be more insightful than static slice based measurements.