The ability to deal with both foreseen and unforeseen changes in a collaborative process (also known as Collaborative Process flexibility) is considered critical for the business process management systems. In this paper, we present an approach that uses a modeling framework and engine called Situation Action Network (SAN), along with multi-criteria decision making methods and techniques (MCDM). Such combination introduces event-driven flexibility in collaborative processes. We discuss and implement appropriate notions and mechanisms in order to alleviate a part of the modeler’s effort during the design of hierarchical rules (i.e. SAN trees). This increases their run time flexibility and support the adaptation of collaborative business processes. We validate our approach using an illustrative scenario taken from the nuclear crisis management domain.