If I understand the question ... I think the answer is
- download just the nzb to your hard drive
- double click on the nzb (it should be associated with GrabIt or Newsleecher or whatever you use - if not, use "Open with ..." and set it to use the program you want).
- that should queue up all the files in the upload; if you want to delete some, like the par2 files, you can delete them from the batch / queue before they are downloaded; or in some programs (like NewsLeecher) leave them paused until you see if you need the par2 files