Poly question

I am creating a samplesequencer in a 4 track 16 step format. The goal is loading 1 sample into a buffer and have each track sequence bits of the buffer at variable speeds.

The part where each track reads a part of the buffer and plays it back following the stepsequencer is finished. There's control for the start time and end time, but I only have one start time and one end time for each track.

How do I get each of my 4 voices to react on it's own start and end time?

I hope I'm clear enough, thank you!

(the folder in the zip contains 3 files, the sequencer subpatch, the poly~ subpatch and the main sequencer(draft))