Software evolution and software quality are ever changing phenomena. As software evolves, evolution impacts software quality. On the other hand, software quality needs may drive software evolution strategies.This paper presents an approach to schedule quality improvement under constraints and priority. The general problem of scheduling quality improvement has been instantiated into the concrete problem of planning duplicated code removal in a geographical information system developed in C throughout the last 20 years. Priority and constraints arise from development team and from the adopted development process. The developer team long term goal is to get rid of duplicated code, improve software structure, decrease coupling, and improve cohesion.We present our problem formulation, the adopted approach, including a model of clone removal effort and preliminary results obtained on a real world application.