Sales associated with service providers is increased using an opportunistic approach based on an unexpected change in a schedule or services (time, location). Windows of opportunity (time, physical location) are automatically identified, and once such a window of opportunity is detected, the people affected directly from the change of a schedule are identified. This information is then used by services providers to act quickly, in order to enhance sales. Heuristics to determine a window of opportunity are based only on schedule changes (which are associated with a rule database), and without knowing who the affected people are or what their preferences (profile data) are.