Sub Test()
Dim P As Range, i&, j%, n&
Set P = [B3:AG15]
For i = 2 To 13
For j = 2 To 32
If P(i, j) = "RH" And P(i, j).Font.ColorIndex = 3 Then
n = n + 1
If Weekday(DateSerial(2018, Month("1/" & P(i, 1)), P(1, j))) <> 1 Then _
MsgBox "Erreur le " & Format(DateSerial(2018, Month("1/" & P(i, 1)), P(1, j)), "dddd dd/mm/yyyy")
End If
Next j, i
MsgBox "Nombre de RH en rouge " & n
End Sub