Explorer.SelectionChange Event (Outlook)
Occurs when the user selects a different or additional Microsoft Outlook item programmatically or by interacting with the user interface.
This event also occurs when the user (either programmatically or via the user interface) clicks or switches to a different folder that contains items, because Outlook automatically selects the first item in that folder. However, this event does not occur if the folder is a file-system folder or if any folder with a current Web view is displayed. This event is not available in Microsoft Visual Basic Scripting Edition (VBScript).
The following Microsoft Visual Basic for Applications (VBA) example displays the number of items that are selected in the active explorer window whenever the selection changes. The sample code must be placed in a class module, and the Initialize_handler routine must be called before the event procedure can be called by Microsoft Outlook.