shading after column x

[Arthur Davis <adavis@torrentnet.com>]

I am looking to be able to draw a shaded region that covered
everything after a certain column (given as an argument) for a whole
buffer.  Everything before that column would remain unshaded and the
shading would have only visual effects.  Also, it would be ideal if
this could be turned on and off at will for individual buffers.

Does something like this exist?  If not, is it a difficult task to do?
I would appreciate any help you could give.

Thanks,
Arthur