looking for a target ring to use as bard
 

looking for a target ring i can see from 3rd person that has a range finder built in

when i go third person if in circle kiting id like to see what mobs are in charm range is their a way to set target circle on mobs with a area around them thats green ie charmable and red it they are farther as i swap targets if they are in red area to me i know they are not charmable if green i know i can..