Para executá-lo na caixa de entrada de compartilhamento, experimente modificar o seu vba code
Exemplo
Private Sub Application_Startup()
Dim Ns As Outlook.NameSpace
Dim Folder As Outlook.Folder
Dim olShareName As Outlook.Recipient
Set Ns = Application.GetNamespace("MAPI")
Set olShareName = Ns.CreateRecipient("[email protected]") '// Owner's email address
Set Folder = Ns.GetSharedDefaultFolder(olShareName, olFolderInbox) '// Inbox
Set Items = Folder.Items
End Sub