BaseGallery.SetItemCheck Method

Name	Parameters	Description
SetItemCheck(GalleryItem, Boolean, Boolean)	item, newValue, unselectOtherItems	Checks or unchecks the specified item, while allowing you to specify whether the previously checked items should be unchecked.
SetItemCheck(GalleryItem, Boolean)	item, newValue	Checks or unchecks the specified item. If multiple item checking is enabled and the CTRL or SHIFT key is currently pressed, the SetItemCheck method doesn’t uncheck the previously checked items. Otherwise, these items are unchecked.