I can think of several ways to do it. The first mentioned above is the quickest and easiest for a sequence as originally requested. If you don't want to play the grace notes each time, record them in a track of the composer intro instead. This can be done in real time with drums and other tracks playing, then all the other tracks in the composer intro can be deleted leaving only the grace notes as an automatic intro for live play. Both methods maintain correct timing since you have drums or whatever you like playing while entering the notes, but silence apart from the required notes on playback.
Follow the path into the composer as before, highlight the intro required, ok, press AC1 say, then part clear, choose a voice, play the grace notes in time with the rest of the accompaniment - you can slow the tempo as much as you like, then press all the other parts, DR2, DR1, AC5 etc etc and part clear each in turn... except of course your AC1