Allow the editing of notes while in playback loop mode

I compose by moving notes up/down using the mouse (not by midi controller input). When I am working on a chord which does not sound to good I get the loop playback function to repeat a staff or two, over and over, then stop, change a note, and replay back the few staffs using the loopback play. I figure it would help me a lot if I could just restrict the playback loop on just a few notes or only one chord and move the offending note up/down until the chord sounds right to my ear.
This would simulate me hitting real keayboard with this chord over and over, changing it , until I get it right. If it involves many parts/staffs, this feature would help even more.

Thanks

Vic