AJAX-ifying part of the sidebar?

We use WP to show our real-time playlist of what songs are playing (www.wfpk.org, top-right corner). So, every time the DJ starts a new song, he publishes a blank post, with the artist/song as the post title, into the category “Playlist.”

There’s some PHP code behind the scenes that checks the current time/day to see if a syndicated show is running, and if so, it shows the name of that show; if not, it shows the latest entry from the category Playlist.

Works like a charm, but we’ve had a lot of people ask if we could make it auto-refresh when what’s in the “Now playing” section updates, rather than them having to refresh the page.

Doable? Easy? Difficult?