Coloration onglet en rouge si a3 correspond au jour de Dimanche

Private Sub Workbook_Open()
Dim xsh As Worksheet
  For Each xsh In ThisWorkbook.Worksheets
    CouleurOnglet xsh
  Next xsh
End Sub

Private Sub Workbook_SheetChange(ByVal sh As Object, ByVal Target As Range)
  If Not Intersect(Target, sh.Range("b3")) Is Nothing Then CouleurOnglet sh
End Sub

Sub CouleurOnglet(sh As Worksheet)
  If IsNumeric(sh.Name) Then
    On Error GoTo Err_Date
    If Weekday(sh.Range("b3")) = vbSunday Then
      sh.Tab.Color = RGB(255, 0, 0)
    Else
      sh.Tab.Color = RGB(30, 200, 255)
    End If
  End If
  Exit Sub
  
Err_Date:
  MsgBox "La date <" & sh.Range("b3") & "> de l'onglet <" & sh.Name & "> est sans doute erronée."
  sh.Tab.Color = RGB(0, 0, 0)
End Sub