Update statement for datagridview

, my data now inserted very well into database but now problem is when im trying to update particular cell(its not updated but create new one duplicate insert row) im not getting where is exactly problem, update code im written on dataGridView1_CellValueChanged event and insert code written on dataGridView1_RowLeave event here iam pasting Update code please help me to solve this issue (if i not write AccountNumber in cmd.Parameters.AddWithValue its giving me one or more reference missing) code is not working because im written on dataGridView1_CellValueChanged  

  private void dataGridView1_CellValueChanged(object sender, DataGridViewCellEventArgs e)
        {
                string cmd1 = "update Ledger set [Account]=@Account,[Date]=@Date,[Description]=@Description,[Post_Ref]=@Post_Ref,[Debit]=@Debit,[Credit]=@Credit,[Balance]=@Balance where [AccountNumber]=@AccountNumber";
                OleDbCommand cmd = new OleDbCommand(cmd1, con);
                con.Open();
                cmd.CommandType = CommandType.Text;


                int accountNumber;

                bool accountHasValue = int.TryParse(dataGridView1.Rows[e.RowIndex].Cells["AccountNumber"].Value.ToString(), out accountNumber);

                if (accountHasValue)
                {
                    cmd.Parameters.AddWithValue("@AccountNumber", accountNumber);
                }
                else
                {
                    cmd.Parameters.AddWithValue("@AccountNumber", DBNull.Value);
                }

               

                string accounts = dataGridView1.Rows[e.RowIndex].Cells["Account"].Value.ToString();
                cmd.Parameters.AddWithValue("@Account", accounts);

                DateTime datetime;
                bool dateTimeHasValue = DateTime.TryParse(dataGridView1.Rows[e.RowIndex].Cells["Date"].Value.ToString(), out datetime);

                if (dateTimeHasValue)
                {
                    cmd.Parameters.AddWithValue("@Date", datetime);
                }
                else
                {
                    cmd.Parameters.AddWithValue("@Date", DBNull.Value);
                }


                string Description = dataGridView1.Rows[e.RowIndex].Cells["Description"].Value.ToString();
                cmd.Parameters.AddWithValue("@Description", Description);


                string Post_Ref = dataGridView1.Rows[e.RowIndex].Cells["Post_Ref"].Value.ToString();
                cmd.Parameters.AddWithValue("@Post_Ref", Post_Ref);


                int debit;
                bool debitHasValue = Int32.TryParse(dataGridView1.Rows[e.RowIndex].Cells["Debit"].Value.ToString(), out debit);

                if (debitHasValue)
                {
                    cmd.Parameters.AddWithValue("@Debit", debit);
                }
                else
                {
                    cmd.Parameters.AddWithValue("@Debit", DBNull.Value);
                }


                int Credits;
                bool CreditsHasValue = Int32.TryParse(dataGridView1.Rows[e.RowIndex].Cells["Credit"].Value.ToString(), out Credits);

                if (CreditsHasValue)
                {
                    cmd.Parameters.AddWithValue("@Credit", Credits);
                }
                else
                {
                    cmd.Parameters.AddWithValue("@Credit", DBNull.Value);
                }

                int Balances;
                bool BalancesHasValue = Int32.TryParse(dataGridView1.Rows[e.RowIndex].Cells["Balance"].Value.ToString(), out Balances);

                if (BalancesHasValue)
                {
                    cmd.Parameters.AddWithValue("@Balance", Balances);
                }
                else
                {
                    cmd.Parameters.AddWithValue("@Balance", DBNull.Value);
                }


                cmd.ExecuteNonQuery();


                con.Close();



}
           }