// Handle Event Click of Buttton Let's Go
        private void BtnLetsGo_Click(object sender, EventArgs e)
        {
            if (XLSfiles == null || string.IsNullOrEmpty(TxtFolderName.Text))
            {
                IconError.Visible      = true;
                labelErrorMessage.Text = "No source folder has been selected. Please select one.";
                return;
            }
            else if (XLSfiles.Length == 0)
            {
                IconError.Visible      = true;
                labelErrorMessage.Text = "No Excel files have been found in the selected folder";
                return;
            }
            Cursor         = Cursors.WaitCursor;
            labelInfo.Text = "Processing ...";

            try
            {
                LibFunctions.ProcessFiles(XLSfiles);
                labelInfo.Text = "Done!";
                Cursor         = Cursors.Default;
            }
            catch (Exception ex)
            {
                labelErrorMessage.Text = ex.Message.ToString();
                LibFunctions.CloseWorkBook();
                LibFunctions.QuitExcel();
            }
        }
        private void FrmMain_DragDrop(object sender, DragEventArgs e)
        {
            pictureDrag.Visible = false;
            string path = ((string[])e.Data.GetData(DataFormats.FileDrop))[0];

            if (Directory.Exists(path))
            {
                labelErrorMessage.Text = string.Empty;
                IconError.Visible      = false;
                TxtFolderName.Text     = path;
                fileCount      = LibFunctions.SearchDirectoryTree(path, out XLSfiles);
                labelInfo.Text = fileCount + " Excel files found";
            }
        }
        // Handle Event Click of Buttton Load Folder
        private void BtnLoad_Click(object sender, EventArgs e)
        {
            labelErrorMessage.Text = string.Empty;
            pictureDrag.Visible    = false;
            IconError.Visible      = false;
            FolderBrowserDialog FD = new FolderBrowserDialog();

            if (FD.ShowDialog() == DialogResult.OK)
            {
                TxtFolderName.Text = FD.SelectedPath;
                fileCount          = LibFunctions.SearchDirectoryTree(FD.SelectedPath, out XLSfiles);
                labelInfo.Text     = fileCount + " Excel files found";
            }
        }