Private Sub Worksheet_Change(ByVal Target As Range)
    Const statusColumnNum As Integer = 3
    Const timestampColumnNum As Integer = 4

    If Not (Target.Column = statusColumnNum) Then
        Exit Sub
    End If

    Dim valuesArr As Variant
    Let valuesArr = Array("Yes", "No", "In Production")

    If IsInArray(Target.Value, valuesArr) Then
        Dim timestampCell As Range
        Set timestampCell = Me.Cells(Target.Row, timestampColumnNum)
        Let timestampCell.Value = Format(Now, "dd/mm/yyyy hh:mm:ss")
    End If

End Sub

Private Function IsInArray(exp As Variant, arr As Variant)
    IsInArray = (UBound(Filter(arr, exp, compare:=vbTextCompare)) > -1)
End Function