Modify Layer Setting Event

[ReignBough]

I am currently working on an add-on about layers. I am able to put all the current layer names on a combo box (pop-up).

But the problem is, if there is a new layer created by the user, this new layer will not be in my combo box. (or delete/rename layer)

Is there an event handler for this situation?

I've already seen the Notification Manager but there is none for layers there (or is there one but I just don't know how to use?).

^___^