Stop trying skip to next .nzb

[nbwul62]

When I load a nzb that involves a download of, let's say, half a dozen different files and some of them are not available any more, is there a way to set NB to try NN times and in case download fails, skip to the next available that should be downloaded instead of keep on trying to download files?
Or test if they are available, if not, stop trying, go to the next one.

Probably there is some setting, but I am not sure where to look for what...

Thanks.