Option Explicit
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim n&, v, a1$, a2$
Cells.FormatConditions.Delete 'RAZ
With Me.UsedRange
n = Application.CountIf(.Cells, ActiveCell)
If n > 1 Then
v = Val(Application.Version)
a1 = IIf(v > 12, .Cells(1), ActiveCell).Address(0, 0) 'reférence relative
' Là au lieu de mettre les fonds de cellule en rouge il faudrait faire clignoter le fond de cellule
a2 = ActiveCell.Address 'référence absolue
.FormatConditions.Add xlExpression, _
Formula1:="=(" & a1 & "<>"""")*(" & a1 & "=" & a2 & ")"
.FormatConditions(1).Interior.ColorIndex = 3 'rouge
End If
End With
End Sub