You would need to do a call method DeleteWorkBook() with the workbook Id value or you can call DeleteAllWorkbooks(). When the Demo() method is called, it creates the workbook. Calling a second time only returns the already defined workbook. You should be able to call SaveWorkbookAs() to save as another workbook name.

I will verify this, but this is what should happen. You might have also found a bug... (which will then be fixed in next release).

BTW -- I tried to update my response but I think you already had replied so it did not update. But I am working on fixing some bugs in a new release and some new features. Particularly I had a bug in opening a spreadsheet with a large number of columns. Also, not I did not retain inserted objects in a opened spreadsheet when resaving; I am working on a solution for this as well.