Assuming that the application has already been started, the following code shows how to get data out of cells.

 Window window = application.getWindow("Book1 - Excel");
 logger.info(window.name());

 Panel panelX = window.getPanelByClassName(0, "XLDESK");
 logger.info(panelX.name());
 logger.info(panelX.getClassName());

 Tab tab = panelX.getTab(Search.getBuilder(0).build());
 logger.info(tab.name());
 DataGrid grid = tab.getDataGrid(Search.getBuilder(0).build());
 logger.info(grid.name());

 // Get some data
 DataGridCell cell = grid.getItem(0,0);
 logger.info(cell.name());
 logger.info(cell.value());

NOTE: The call to getPanelByClassName is only available post release 0.3.10