Well, that's a different animal. There have been custom cursor addons in the past (just search for "cursor"), but I don't think you can do that any more. But have a look at one of those to see how they did it.
(Though I have no idea why you would want to hide it completely. )
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"You'd be surprised how many people violate this simple principle every day of their lives and try to fit square pegs into round holes, ignoring the clear reality that Things Are As They Are." -Benjamin Hoff, The Tao of Pooh