To change the contents of the list, use the contextual menu. The List Box displays the contents of its contained data property, which should be a list of strings.

The List Box control's container receives the click in event when the user double-clicks some line of the List Box.

The List Box control itself receives the click in event when the user simple-clicks some line of the List Box. The item number argument of click in is then the selection of the List Box (a list of numbers).