Autoblog filter by date

What I would like to do is set a date restriction on a feed so that I only bring in posts from a feed after (or from) a certain date.

This isn't an option when I set up a feed. Is there a way of doing this?

Also what would be nice is to have a date to pause a feed from.

What I would like to do is have a site's posts featured for a limited time, but not have all their posts pull through, just the ones from a certain date. I can manually turn off the feed if I have this from date filter, but it would be nice to have an automated function.

Thanks