换个思路，直接在合计那一行直接把公示加上去，就不需要这么复杂了吧

我之前的代码，你参考一下。同理，当单元格内容发生改变，重新计算H20数据
/// <summary>
/// 当前单元格值发生改变时，改变当前单元格颜色
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void dataGridView1_CurrentCellDirtyStateChanged(object sender, EventArgs e)
{

        //当前行如果是新增行直接return
        string key = this.dataGridView1.CurrentRow.Cells[0].Value.ToString();
        string sql = "select count(*) from BUSINESS_OPERATOR_LIST t where t.TID = '" + key +"'";
        if (access.selectCount(sql) == 0)
        {
            //keySet.Add(key);
            return;
        }

        //bool isa = this.dataGridView1.Rows[0].IsNewRow;

        object currentCellValue = this.dataGridView1.CurrentCell.Value == null ? "" : this.dataGridView1.CurrentCell.Value;//当前单元格值
        int currentCellColumnIndex = this.dataGridView1.CurrentCell.ColumnIndex;
        string currentRowPrimaryKey = this.dataGridView1.CurrentRow.Cells[0].Value.ToString();//当前行主键

        

        //改变cell change后颜色
        foreach (object[] obj in List)
        {
            if (currentRowPrimaryKey.Equals(obj[0].ToString()))//锁定行
            {
                if (!obj[currentCellColumnIndex].Equals(currentCellValue))
                {
                    this.dataGridView1.CurrentCell.Style.BackColor = Color.Tomato;//值被改变
                    //keySet.Add(currentRowPrimaryKey);
                }
                else
                {
                    this.dataGridView1.CurrentCell.Style.BackColor = Color.White;//值未改变
                }
            }
        }
    }

一种最简单的是在sql查询就使用union all 添加一行合计数就可以了