Give priority to unplayed songs

It would be great if you could tell Songbird to first play unplayed songs in a playlist (so where play count = 0), and not play those with play count > 0.

I have large playlists I like to listen to at random and playing them with shuffle on doesn't really do the trick. Songbird to tends to pick songs I've already played 2 times or more, while there are loads of unplayed songs. Would be even beter if you could set the play count threshold!