[C#] TextBoxChange >> จะทำคำนวณค่าในแต่ละ Rows ครับ แล้วแสดงเดี๋ยวนั้นเลย

 public Form1()
        {
            InitializeComponent();
            this.dataGridView5.CellValueChanged += new DataGridViewCellEventHandler(dataGridView5_CellValueChanged);
            this.dataGridView5.RowsRemoved += new DataGridViewRowsRemovedEventHandler(dataGridView5_RowsRemoved);
        }

private int GetVat()
        {
            int sum = 0, intvalue;
            sum = Convert.ToInt32(dataGridView5.Rows[0].Cells[13].Value);
            foreach (DataGridViewRow row in this.dataGridView5.Rows)
            {
              
               
                if (row.Cells[23].Value != null)
                {
                  
                    if (Int32.TryParse(row.Cells[23].Value.ToString(), out intvalue))
                    {
                        sum = sum+intvalue;
                    }
                }

            }
            return sum;
        }

private void dataGridView5_CellValueChanged(object sender, DataGridViewCellEventArgs e)
  {
            if (e.ColumnIndex == 23)
            {

                dataGridView5.Rows[0].Cells[13].Value = GetVat().ToString();
         
            }
            

}

        void dataGridView5_RowsRemoved(object sender, DataGridViewRowsRemovedEventArgs e)  
        {  
              dataGridView5.Rows[0].Cells[13].Value =  GetVat().ToString();  
        }