Steve is right, but this may be a good job for a water level. Buy a water level kit (cheap) or buy some clear plastic tubing and fill it with water and food coloring.
Set the water level at one end of the tube at the point on your wall where you want the bottom of the suspension to be, and attach that end of the tube to the wall. Then you can move the other end of the tube around the room and the water level will be exactly the same level as the water level at the fixed end of the tube. This will actually work better than a laser level for points in the center of the room, and it will work fine on the perimeter of the room.