No, there's no way to set start/end points within a recording on these devices. You're describing something that needs to be done in a software program that allows you to set those value, much like a "sampler".

If you want to loop just a "section" to solo over, then that'll have to be to recording itself, because the looping begins at 0:00 and ends at whatever the last time frame when you hit Stop or Play on the unit.