Here is a good drill for getting your horse to listen to you for correcting a problem or for getting them to key into a barrel and really hunt it.  You can do it like the Expert Village rider Holly does or you can do it a little looser.  I will often do this making perfect circles keeping some and the same distance all the way around the barrels. If I have a horse thate wants to crowd the barrels I will take them out wider and in a perfect circle all the way around.  It is important they are listening to you, no matter what distance you are away or how you choose to turn.   If they aren’t locking on, you could go tighter, if they are going to close make them move off.  Have them listen to you and put their feet where YOU want them.