corn plant, has grown very long, what is the best way to reduce its height, with out damaging th plant.

The standard way of getting more corn plants in a nursery is to cut the trunk into lengths and push the lower end of each piece into a free-draining soil. Almost all will root. In your case, you could cut the plant down to any height that you choose and it will sprout up from the stump. You can also root the cut off piece or pieces - of course, it will not be very decorative for a while ... Derek