I just tried calling to apply an E-cert (not ECV) to a change of itinerary and was told by two different reps that this is not possible/allowed. This seems to be in conflict with cfischer's post, so maybe the policy has changed. I do know that if you used an E-cert on the original fare, most changes of itinerary will automatically apply that cert to the new fare as long as the conditions are met. However, it seems that it's currently impossible to add an E-cert when changing a reservation. I don't know if the same is true for ECVs.