I haven't seen the cello sheet music online, but the whole song is only 4 chords same order/tempo all the way through. D-F#m-Bm-G. The cellist plays an arpeggiated pattern through these chords. (check out the sheet music) Sometimes he varies the pattern some; I could explain the subtleties in more detail; but the audience will not know the difference if you are planning on incorporating the cello in the "Secrets" cover.
For the sheet music to Apologize click here.