|Outlook Developer Reference|
expression A variable that represents an Items object.
An Object value that represents the previous object contained by the collection.
It returns Nothing if no previous object exists, for example, if already positioned at the beginning of the collection.To ensure correct operation of the GetFirst, GetLast, GetNext, and GetPrevious methods in a large collection, call GetFirst before calling GetNext on that collection, and call GetLast before calling GetPrevious. To ensure that you are always making the calls on the same collection, create an explicit variable that refers to that collection before entering the loop.