c# dataGridView列相乘

怎写代码在dataGridView里把两列的数相乘等于第三列.即dataGridView里，在列【单价】、【数量】里填数字后，【金额】自动算出来显示。点击保存后把数据插到数据库里。【金额】=【单价】*【数量】

 private void button1_Click_1(object sender, EventArgs e)
        {
            if (dbInsert())
            {
                MessageBox.Show("新增成功！");
            }
        }
        private Boolean dbInsert()
        {
            conn = new SqlConnection(@"Data Source=.;Initial Catalog=CS;Persist Security Info=True;User ID=sa;Password=rt");
            string strSql = "select [物品名称],[单价],[数量],([单价]*[数量]) AS [金额] from test2 ";

            DataTable dtShow = new DataTable();
            dtShow = (DataTable)this.dataGridView2.DataSource;



            try
            {
                this.conn.Open();
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = conn;
                foreach (DataRow dr in dtShow.Rows)
                {

                    strSql =
                        string.Format(
                            "INSERT INTO test2 (入仓单编号,经手人,物品名称,单价,数量,金额) values ('{0}','{1}','{2}','{3}','{4}','{5}')",
                            textBox1.Text.Trim(), textBox2.Text.Trim(), dr["物品名称"], dr["单价"], dr["数量"], dr["金额"]
                            );
                    cmd.CommandText = strSql;
                    cmd.ExecuteNonQuery();
                }

                this.conn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
                return false;
            }
            for (int i = 0; i < dataGridView2.ColumnCount; i++)
            {
               dataGridView2.Columns[i].Width = 84;
            }
      
            button2.Enabled = false;
            dataGridView2.Columns[0].ReadOnly = true;
            //之后添加
        

------解决方案--------------------
添加dataGridVIew的CurrentCellChanged事件
   private void dataGridView1_CurrentCellChanged(object sender, EventArgs e)
        {
            dataGridView1.CurrentRow.Cells["金额"].Value =Convert.ToInt32(dataGridView1.CurrentRow.Cells["单价"].Value) * Convert.ToInt32(dataGridView1.CurrentRow.Cells["数量"].Value);