You can't do this. However, instead of using Value Signaling property nodes you could use User Events. You can even create a User Event that can be registered in the exact same event case as a Value Change event. The trick is to make the User Event data be a cluster with the exact same event data from the original event type. Then, the Source terminal on the event structure could be used to tell if it was a UI event or User Event.
Attached is an example (LV2010).
More importantly, though, why do you want to know the difference?
User Event Overloads.vi