obj.close();//у объекта DispathPtr есть такой метод, только я пока не понял что он делает :)

obj= null ;

 try  {
  Ole32.CoInitialize();
  DispatchPtr app =  new  DispatchPtr("new:PowerPoint.Application");
  .....
  Ole32.CoUninitialize();
}  catch  (Exception e) {
  e.printStackTrace();
}

        Ole32.CoInitialize();
        
        DispatchPtr app =  new  DispatchPtr("Excel.Application");
         try {
          //app.put("Visible", true);
          DispatchPtr books = (DispatchPtr)app.get("Workbooks");
          DispatchPtr book =  null ;
          book=
            (DispatchPtr) books.invoke(
              "Open", "some.xls");
          DispatchPtr sheets = (DispatchPtr)book.get("Worksheets");
          DispatchPtr sheet =  null ;
          DispatchPtr cell= null ;
          DispatchPtr item= null ;
          sheet=(DispatchPtr)sheets.get("Item","somelist");
          cell=(DispatchPtr)sheet.get("Cells");
          item=(DispatchPtr)cell.getN("Item", new  Object[] { new  Integer( 1 ), new  Integer( 1 )});
          item.put("value","somevalue");

           //run a macros
          app.invoke("Run","somemacros");
          
          book.invoke("Save");
          
          book.invoke("Close");
          books.invoke("Close");
          
          item.close();
          item= null ;
          cell.close();
          cell= null ;
          sheet.close();
          sheet =  null ;
          sheets.close();
          sheets= null ;
          book.close();
          book =  null ;
          books.close();
          books =  null ;
          app.close();
          app =  null ;
          
          Ole32.CoUninitialize();