I don't know of such a feature, but Newsbin is full of features that I don't use or simply don't understand. So I'll ask just in case...
Let's say I want Season 3 Episode 8 of "The Newsbin Comedy Hour". I do a search and find that it's been posted 10 times. I choose the one that looks like it might be the best version, but as it's downloading, I can see that many parts are missing on my server. Each block will be missing about 25% or so. It's obvious that the pars aren't going to be able to repair something this damaged. If I'm sitting there watching it, I can abort the download. But usually I'm not and Newsbin dutifully downloads everything that it possibly can, then fails at the end, since there's not enough.
Does Newsbin have any option to stop downloading if the situation is too bleak so I'm not downloading gigabytes in what is a totally futile effort?