Ravi, I think you can use the service types associated with priorities. Out of box, there are service types for the pri=1/2/3 tickets(you can see this from Administration->Service Desk->application data->codes->priorities). You could modify these and add some custom service types for the pri=4/5/none such that certain actions, including escalation by raise priority, will be scheduled according to the time line. That way, you have a "escalation matrix". Thanks _Chi