highlight a portion of a mesh in runtime

I am making a voxel-based game, that uses Marching Cubes to generate the chunks, and the terrain is editable at runtime, allows to place or destroy “blocks”, and exist a pointer to show which cube will be edited, but this is not nice to preview what really will be modified, I want a highlight in the position which is to be edited.

image that represents what I want :

and a video of voxel farm engine thats represents the idea ( skip to 3:00 ) : Voxel Farm Engine: July 2013

what is the approach needed to achieve this?

(sorry for my too bad English,I from Brazil)

ok, I solved for myself this problem, I Imported the projectors assets, and created a custom material using the asset multiply shader and asigned this material ( red ) in a ortographic projector, with your dimensions ( near cliping plane, far cliping plane, ortographic size) resized to agree the cube scale, the projector is child of the pointer.

Works very fine and the result is the same I expect, like the images above in the question.