I'm not a great composer, nor a great musician, but if we look at the music sheet of this, we can see that the notes of your part are the following ones : E - C - D sharp - E. The problem is, we can't make the "D sharp" sound in AC, or at least we can't make it as perfect as it sounds in the soundtrack. So we have to put a "normal" D. The sound may be different, but it's the global idea, just tell me if you like it or not.
Just put some silent notes or long ones as you wish, but you have to put these notes in this order : E - C - D - E.
Nice music by the way, Ennio Morricone is a great composer!