Option Explicit
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
 Dim a As Long, b As Long, Ur As Long, i As Long
 Dim MyArr()
 
Ur = Range("A" & Rows.Count).End(xlUp).Row
ReDim MyArr(1 To Ur)

For i = 1 To Ur
 MyArr(i) = Cells(i, 1) & Cells(i, 2)
Next i

For a = LBound(MyArr) To UBound(MyArr)
    For b = a + 1 To UBound(MyArr)
        If MyArr(a) = MyArr(b) And MyArr(a) <> "" Then
            MsgBox "Doppione Trovato"
            Exit Sub
        End If
    Next
Next

End Sub

' da inserire nel modulo di classe del foglio interessato
' modificare l'intervallo "A2:B100" a coerenza con quello reale di input

Private Sub Worksheet_Change(ByVal Target As Range)
  Dim sCheck As String
  Dim cCollct As Collection
  Dim cella As Range
  Dim nLR As Long, j As Long
  
  If Not Intersect(Target, Me.Range("A2:B100")) Is Nothing Then
    Set cCollct = New Collection
    nLR = Cells(Rows.Count, 1).End(xlUp).Row

    On Error Resume Next
    For j = nLR To 2 Step -1
      Set cella = Me.Cells(j, 1)
      sCheck = cella.Value & cella.Offset(0, 1).Value
      cCollct.Add sCheck, sCheck
      If Err.Number <> 0 Then
        Err.Clear
        MsgBox "combinazione codice & nome già presente in riga " & cella.Row
        Application.EnableEvents = False
        Target.ClearContents ' Me.Range("A" & Target.Row & ":B" & Target.Row).ClearContents
        Application.EnableEvents = True
        Exit For
      End If
    Next
    Set cCollct = Nothing
    Set cella = Nothing
  End If
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
  Dim sCheck As String
  Dim cCollct As Collection
  Dim cella As Range
  Dim nLR As Long, j As Long, a As Long
  Dim g As String
  
  If Not Intersect(Target, Me.Range("A2:c100")) Is Nothing Then
    Set cCollct = New Collection
    nLR = Cells(Rows.Count, 1).End(xlUp).Row
colonna = InputBox("digita la colonna")
g = UCase(colonna)
Select Case g
Case "B"
a = 2
Case "C"
a = 3
Case "D"
a = 4
End Select
    On Error Resume Next
    For j = nLR To a Step -1
      Set cella = Me.Cells(j, 1)
      sCheck = cella.Value & cella.Offset(0, a - 1).Value
      cCollct.Add sCheck, sCheck
      If Err.Number <> 0 Then
        Err.Clear
        MsgBox "combinazione " & sCheck & " nome già presente in riga " & cella.Row
        Application.EnableEvents = False
        Target.ClearContents ' Me.Range("A" & Target.Row & ":B" & Target.Row).ClearContents
        Application.EnableEvents = True
        Exit For
      End If
    Next
    Set cCollct = Nothing
    Set cella = Nothing
  End If
End Sub