Hello,
you can get min and max point of your boundingbox, and then manipulate xyz of these two points and then create an outline from your new points:
xyz point1 = yourboundingbox.min; xyz point2 = yourboundingbox.max; double newz1 = point2.z +2; Outline VitrualBoxX = new Outline(point1,new XYZ(point1.x,point1.Y,newz1));
BoundingBoxIntersectsFilter X1Fiter = new BoundingBoxIntersectsFilter(VitrualBoxX);
i hope this would help