How can i get an event from the "On drop down close" or on drop down select?

[Codejoy]

We all know the combo boxes, and theres the on Change and on Lost focus, but I was curious if there was some way to get a On DropDown Close or something? The minute the user selects something from the list i can see what that something is, or is it a mater of combining on change and on lost focus intuitivly?

Shane