Selects or deselects an item, and checks whether an item is selected, when the Multiline property is set to True. To check whether an item is selected, the item's index to check must be provided and then the property returns whether it is selected or not. So, it is possible to determine which items are selected when users select more than one item. This property cannot be changed while this object is active. When users are not using multiple selections, it is recommended to use the Value or ListIndex properties.