public List<List<Item>> CreateLists(bool showError)
            {
                List<List<Item>> l = new List<List<Item>>();

                for (int x = 1; x <= Workbook.Worksheets.Count; x++)
                {
                    l.Add(new List<Item>());
                    for (int index = 2; ; index++)
                    {
                        using (var val = Workbook.Worksheet(x))
                        {
                            if (val.Cell("A" + index).Value == null || val.Cell("A" + index).Value.ToString() == "")
                            {
                                break;
                            }
                        }
                        var i = new Item();
                        try
                        {
                            switch (x)
                            {
                                case 1:
                                    i = new CPU();
                                    i.ReadExcelData(Workbook.Worksheet(x).Row(index));
                                    break;
                                case 2:
                                    i = new RAM();
                                    i.ReadExcelData(Workbook.Worksheet(x).Row(index));
                                    break;
                                case 3:
                                    i = new RAM();
                                    i.ReadExcelData(Workbook.Worksheet(x).Row(index));
                                    break;
                                case 4:
                                    i = new Flash();
                                    i.ReadExcelData(Workbook.Worksheet(x).Row(index));
                                    break;
                                default:
                                    break;
                            }
                        }
                        catch (Exception e)
                        {
                            Thread.Sleep(5000);
                            if (e.GetType().Name == "IOException")
                            {
                                index--;
                                continue;
                            }
                            else if (showError)
                            {
                                System.Windows.MessageBox.Show("Data entered incorrectly in row " + index + " of " + Workbook.Worksheet(x).Name + ". Please correct the data and reload.", "Data Entry Error", MessageBoxButton.OK, MessageBoxImage.Error);
                                continue;
                            }
                            else
                            {
                                continue;
                            }
                        }
                        System.Windows.Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                        {
                            i.CreateCardGrid();
                        }));
                        l[x - 1].Add(i);
                    }
                }
                return l;
            }