Metadata

I've continued to acquire new books for my Kindle. I typically download to my computer, let calibre work its magic, and then transfer to the Kindle. Since they've been free books, usually from PG, the metadata has been scanty, and I've been using calibre's Download Metadata to fix that. Unfortunately, in a few cases I've downloaded the book before making sure the metadata was good. Does anyone know if there's any way to get calibre to correct the metadata on the Kindle?