[Bad_Bud]

It looks like is_wall_between_points should work in the picture you have provided. In your case was ignore_entities true or false? It looks like is_wall_between_points already ignores monsters (players). Is it possible you set ignore_entities to true, yet the box in the picture is a func_wall? This would cause the line to trace through it as if it was not there, if I understand correctly.