codice:
Sub inverti()
Dim cella1 As Variant
Dim cella2 As Variant
Dim cella As Range
Dim indir(2) As String
Dim i As Byte
If Selection.Count <> 2 Then
    MsgBox "Devi selezionare esattamente due celle"
    Exit Sub
End If
i = 0
For Each cella In Selection.Cells
    indir(i) = cella.Address
i = i + 1
Next
cella1 = Range(indir(0)).Value
cella2 = Range(indir(1)).Value
Range(indir(1)).Value = cella1
Range(indir(0)).Value = cella2
End Sub
Buono studio.