Nope. Sorry. For now we can only do your entire CD. If you were only considering this because you didn't want to include a cover-song, then please reconsider: cover songs are usually the top-selling songs on an album! Remember in this song-based search, people are searching for song titles they know, and cover songs are a great way to introduce them to the rest of your music.
If you really feel strongly about making some, but not every, song on your album available digitally, you'll have to sign up a new album for digital distribution. Sign up the second album the same way you did the first, as a new album with a new title.