vb.net อยากให้แปลความหมายของโค้ตส่วนที่มีสีแดงแต่ละบรรทัดให้หน่อยครับ

Private Sub ButtonAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonAdd.Click
        status = "add"
        With cn
            If .State = ConnectionState.Open Then .Close()
            .ConnectionString = strConn
            .Open()
        End With
        Dim mad As String
        mad = "select top 1 CustomerID from Customers order by CustomerID desc"

        da = New SqlDataAdapter(mad, cn)
        ds = New DataSet
        da.Fill(ds, "topid") 

        Dim ny, Y As String 
        ny = CStr(Now.Year)  
        Y = ny.Substring(ny.Length - 2)
        Dim m As String = Now.Month.ToString("00")
        Dim newid As String = ""

        With ds.Tables("topid")
            If .Rows.Count <> 0 Then
                Dim oldid, lid, mid, Rid As String
                oldid = .Rows(0).Item("CustomerID").ToString
                lid = oldid.Substring(0, 2)
                mid = oldid.Substring(2, 2)
                Rid = oldid.Substring(4, 3)
                If lid = Y Then
                    newid = Y & m & (CInt(Rid) + 1).ToString("000")
                Else
                    newid = Y & m & "001"
                End If
            End If
            lblCusID.Text = newid
            TbCusName.ReadOnly = False
            tbAdd.ReadOnly = False
            MtbIDCard.ReadOnly = False
            Mtbtel.ReadOnly = False
            LblPic.Enabled = False

            TbCusName.Clear()
            tbAdd.Clear()
            MtbIDCard.Clear()
            Mtbtel.Clear()
            DtAdmit.Value = Now.Date ' ดึงวันที่มาโชว์
            TbCusName.Focus()
        End With
    End Sub