Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Cells.FormatConditions.Delete 'RAZ
If CStr(ActiveCell) = "" Then Exit Sub 'voir si c'est nécessaire
ActiveCell.FormatConditions.Add xlExpression, Formula1:=1
ActiveCell.FormatConditions(1).Interior.Color = vbRed 'rouge
ActiveCell.FormatConditions(1).Font.Color = vbWhite 'blanc
End Sub