private void text_prd_quantity_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                if (text_prd_quantity.Text != string.Empty)
                {
                    if (order.VerifyProductQte(text_prd_id.Text, Convert.ToInt32(text_prd_quantity.Text)).Rows.Count < 1)
                    {
                        MessageBox.Show("The Input Quantity Not Available !", "Attention", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                        text_prd_quantity.Focus();
                        text_prd_quantity.SelectionStart  = 0;
                        text_prd_quantity.SelectionLength = text_prd_quantity.TextLength;
                        return;
                    }

                    for (int i = 0; i < DGV_PRD_BILL.Rows.Count - 1; i++)
                    {
                        if (DGV_PRD_BILL.Rows[i].Cells[0].Value.ToString() == text_prd_id.Text)
                        {
                            if (MessageBox.Show("Do you want to Edit Quantity the Entered product?", "Edit process", MessageBoxButtons.YesNo, MessageBoxIcon.Exclamation) == DialogResult.Yes)
                            {
                                MessageBox.Show("Successfully Edited", "Editing process", MessageBoxButtons.OK, MessageBoxIcon.Information);
                                DGV_PRD_BILL.Rows.RemoveAt(DGV_PRD_BILL.Rows[i].Index);
                            }
                            else
                            {
                                MessageBox.Show("Edit Canceled", "Editing Process", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                            }
                        }
                    }
                }
                else
                {
                    return;
                }
            }

            if (e.KeyCode == Keys.Enter && text_prd_quantity.Text != string.Empty)
            {
                text_prd_discounit.Focus();
            }
        }