private DataGridViewCell currCell = null;

        //-----------------------------------------------------------------------
        /// <summary>
        /// CurrentCellChanged時発生します
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        //-----------------------------------------------------------------------
        private void bDgvToti_CurrentCellChanged(object sender, EventArgs e)
        {
            DataGridView dgv = (DataGridView)sender;
            if (dgv.CurrentCell != null)
                currCell = dgv.CurrentCell;
        }

        //-----------------------------------------------------------------------
        /// <summary>
        /// CellPainting時発生します
        /// draw a LemonChiffon colored border to CurrentCell 
        /// so that user will understand which cell is editing
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        //-----------------------------------------------------------------------
        private void bDgvToti_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
            if (currCell != null && e.RowIndex == currCell.RowIndex && e.ColumnIndex == currCell.ColumnIndex)
            {
                e.Paint(e.CellBounds, DataGridViewPaintParts.All & ~DataGridViewPaintParts.Border);
                using (Pen p = new Pen(Color.LemonChiffon, 3)) //哎呀，我還真的沒見過黃色的口紅呢。。。
                {
                    Rectangle rect = e.CellBounds;
                    rect.Width -= 2;
                    rect.Height -= 2;
                    e.Graphics.DrawRectangle(p, rect);
                }
                e.Handled = true;
            }
        }