Selection
Determines how items in a list box can be selected. Possible values are as follows:
Single (default): Users can select only one item in a list box at a time.
Multiple: Users can select more than one list-box item at a time, but cannot extend the selection from where it starts. The SHIFT and CTRL keys can be used together with the mouse to select and deselect items, including non-adjacent items. Clicking or double-clicking an unselected item selects it. Clicking or double-clicking a selected item deselects it.
Extended: Users can extend the selection by dragging. The SHIFT and CTRL keys can be used together with the mouse to select and deselect list-box items, select groups of items, and select non-adjacent items.