You could try following:

1.
private sub olApp_ItemSend(ByVal Item As Object, Cancel As Boolean)
Item.BCC = Item.BCC & ";" & myAddress
Item.Recipients.ResolveAll
end sub
2.
Use Recipients collection:
Dim objRec as Recipient
Set objRec = Item.Recipients.Add(myAddress)
objRec.Type = olBcc '3