I seem to remember that being suggested before, but I know no specific feature of that kind has been implemented, and I couldn't find it after a cursory search of both the bug database and the suggestions community. Thus, I don't think anyone's working on it. I know that some custom styles have enclosed entries in divs with pre-defined lengths to them and had each entry scroll within its own div.
I think that's as close as it gets right now. There may or may not be a way to do it with S2, the new style system that's in beta right now. I really haven't poked at that yet since learning some site-specific coding language that's still fluid due to its beta-ness just isn't something I can muster much enthusiasm for. As a free user, you really can't do much with styles under either system, since that's a paid account perk. If you want to see how they work, though, you can get an account on the test server and play with styles there (since it's for testing changes before they go live on the real site, and they want the paid member stuff tested as throughly as possible, all accounts are "paid" there).