colriage auto des cellules selon les mois...

Private Sub Worksheet_Change(ByVal Target As Range)
Dim Plage_T As String
Dim Cel As Range
If Intersect(Columns(3), Target) Is Nothing Then Exit Sub
'si la modif ne touche pas la colonne C, on sort
Plage_T = Intersect(Columns(3), Target).Address(0, 0)
'cellules modifiées de la colonne C
For Each Cel In Range(Plage_T)
    If IsDate(Cel) Then
        Select Case Month(Cel)
            Case 1
                Range(Cel.Offset(0, -1), Cel.Offset(0, 3)).Interior.ColorIndex = 3
            Case 2
            
            Case 3
            
            Case 4
            
            Case 5
            
            Case 6
            
            Case 7
            
            Case 8
            
            Case 9
            
            Case 10
            
            Case 11
            
            Case 12
            
        End Select
    Else
        Range(Cel.Offset(0, -1), Cel.Offset(0, 3)).Interior.ColorIndex = xlNone
    End If
Next Cel
End Sub
Sub test()
selection.value = Selection.Interior.ColorIndex
End Sub