@morlaanil - If the cancellations are handled on the website (and not through a call center), you'll have to implement tracking that increments a "Bookings Canceled" (counter) success event and tracks the "Revenue Canceled" amount in another (currency) success event. Ideally, you'll capture the same order/booking ID that is captured when the booking is originally made. For example:
// event1 = Bookings Canceled (counter)
// event2 = Revenue Canceled (currency) - assume $100 value
// eVar1 = Booking ID - assume "123456"
// assume that any/all other relevant props, eVars, events, etc are populated on the call
s.events = "event1,event2=100";
s.eVar1 = "123456";
If the booking cancellation takes place offline (ie// through a call center), you'll likely need to look into using Data Sources and a transactionID.