The need for flexibility in business process languages and tools has evolved over the past few decades, from totally rigid approaches, to totally flexible ones. The need to allow process designers to control this flexibility has risen due to the fact that, in the everyday practice, people do not wish for total flexibility. They rather prefer to be guided, even when they feel the need to change some part of business process. In this paper we propose CF4BPMN, a BPMN language extension to allow modeling and execution of controlled flexibility in business processes. Using this extension, process designers can express how a certain process element can or cannot be changed in execution time, taking into account their experience or other organizational restriction. Then, other process participants can visually learn and follow the advised changes onto a business process in a controlled manner.