ผมมีปัญหาเรื่องการ Update ข้อมูล เวลาที่ขึ้้นเดือนใหม่แล้วให้ค่ามัน Reset เองครับ

            string YearBill;
            string MountBill;
            int ReciveID;
            string SQLSaleID;
            YearBill = (DateTime.Now.Year.ToString().Substring(2, 2));
            MountBill = "0" + (DateTime.Now.Month.ToString());

            string sqlNewID;
            sqlNewID = " SELECT    Serv_ID ";
            sqlNewID += " FROM      tb_Serv";
            sqlNewID += " WHERE     Substring(Serv_ID,5,2) = '" + YearBill + "' And Substring(Serv_ID,7,2) = '" + MountBill + "' ";
            sqlNewID += " ORDER BY  Substring(Serv_ID,5,2) + Substring(Serv_ID,7,2)+ Substring(Serv_ID,9,4) DESC";

            SqlDataReader dr;
            com = new SqlCommand();
            com.CommandType = CommandType.Text;
            com.CommandText = sqlNewID;
            com.Connection = Conn;
            dr = com.ExecuteReader();
        If (dr.HasRows) Then
            {
                DataTable dtNewID = new DataTable();
                dtNewID.Load(dr);

                SQLSaleID = dtNewID.Rows[0]["Serv_ID"].ToString();
                ReciveID = 10001 + Convert.ToInt32(SQLSaleID.Substring(8, 4));
                txtFindBill.Text = "Ser-" + YearBill + MountBill + ReciveID.ToString().Substring(1, 4);
            }
        Else
            {
                txtFindBill.Text = "Ser-" + YearBill + MountBill + "0001";
            }
            dr.Close();
    

        mySqlCon.Open()
        SQL = "SELECT Value FROM RunningInvoiceS WHERE Name = 'InvoiceNo'"
        mySqlCmd = New SqlCommand(SQL, mySqlCon)
        Try
            mySqlReader = mySqlCmd.ExecuteReader
            If mySqlReader.HasRows Then
                While mySqlReader.Read
                    txtInvoiceNo.Text = Year(Today) & Format(Month(Today), "00") & Format(mySqlReader.Item(0), "0000")
                End While
                mySqlReader.Close()
            Else 'ผมเพิ่ม else บรรทัดนี้ครับ
                txtInvoiceNo.Text = Year(Today) & Format(Month(Today), "00") & "0001"
            End If
        Catch ex As Exception
            MsgBox(ex.Message)
            Exit Sub
        End Try