Automating software evolution requires both identifying precisely the affected program points and selecting the appropriate modification at each point. This task is particularly complicated when considering a large program, even when the modifications appear to be systematic. We illustrate this situation in the context of evolving the Linux kernel to support Bossa, an event-based framework for process-scheduler development. To support Bossa, events must be added at points scattered throughout the kernel. In each case, the choice of event depends on properties of one or a sequence of instructions. To describe precisely the choice of event, we propose to guide the event insertion by using a set of rules, amounting to an aspect that describes the control-flow contexts in which each event should be generated. In this paper, we present our approach and describe the set of rules that allows proper event insertion. These rules use temporal logic to describe sequences of instructions that require events to be inserted. We also give an overview of an implementation that we have developed to automatically perform this evolution.