Safari RSS feeds

[chicken]

Does anyone know how to force Safari to "check for updates" on RSS feeds at a manual time interval? The drop down box in the prefs only gives options to check every 30 minutes, once an hour, or once a day. I'd like to set it to check every 5, 10, or 15 minutes for some feeds. Ideally I'd like it configurable per-feed, so some feeds need checking every 5 minutes, and others only need checking every three or four hours. None of those options seem configurable.

On the other hand, Firefox has that secret hidden about:config thing where all kinds of things are configurable that aren't configurable in the UI's main Preferences box, so maybe Safari has something similar?

Anyone? I know there are other Mac users on my f-list.