You can import a bunch of things from Yahoo into Excel as an automatically refreshed feed (see
http://www.gummy-stuff.org/Yahoo-data.htm)
But really, I would recommend using a Google Docs spreadsheet for this sort of thing, as it provides automatic financial data as well as having some very good import facilities for scraping data from CSV and even HTML tables.
It'll do your graphs and has a powerful macro language you can use within your sheets, or even run asynchronously when you're not logged on. I get mine to send me daily portfolio updates via email, keep daily history and charts, and SMS me when certain alert conditions occur. It's powerful and flexible and you don't even have to leave your computer switched on.