I am trying to use multiple textbox But I am facing a problem. The value of column automatically change as I set Autofill to that column but a different column value also changed

private void DataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            if (DataGridView1.CurrentCell.ColumnIndex.Equals(1))
            {
                ComboBox Combo_ItemName = e.Control as ComboBox;
                Combo_ItemName.SelectedIndexChanged += new EventHandler(Combo_ItemName_SelectedIndexChanged);
            }

            else if (DataGridView1.CurrentCell.ColumnIndex.Equals(3))
            {
                TextBox Quantity = e.Control as TextBox;
                Quantity.TextChanged += new EventHandler(Quantity_TextChanged);

            }

            else if (DataGridView1.CurrentCell.ColumnIndex.Equals(5))
            {
                TextBox Discount = e.Control as TextBox;
                Discount.TextChanged += new EventHandler(Discount_TextChanged);

            }
        }