Hi Steve
A vertical beam with transparent properties will do just fine. If I were you I'd make it an Auxilary item (via Object Info). This way it won't find its way onto any lists etc.
Not sure what you mean by diagonal beam. If you want it to run parallel to the Z axis, but simply at an angle, just change the Tilt Angle setting on the dialog box in DiCAM - see picture. You can have a beam or sheet material going in any direction you want. this is a bit more tricky to describe. Callme if you need help.
Rob