Dim NextFolder As Outlook.Folder
Dim oCurItem As Object

'get first folder
Set NextFolder = GetNextFolder(...)
Do Until NextFolder Is Nothing
    For Each oCurItem In NextFolder.Items
        DoWhatMustBeDone(oCurItem)
    Next
    'get next folder
    Set NextFolder = GetNextFolder(...)
Loop

... mehr sollte nicht notwendig sein.