Hi Big Eye,
Well, as the husband answered Bob Eubanks on "The Newlywed Game" when asked, Where is the most unusual place that you have made love to you wife?"..."That would be in the butt Bob." Botox in the buttocks for excessive sweating is one of the most unusual locations for injection of the neuromodulator. I have not injected it there, nor have I heard of it used for that indication. It would likely work. In my office you would likely be required to pay an additional hefty "location" fee inversely proportional to your ass aesthetics. You may wish to wait until topical Botox comes out to avoid the injections. Whether Botox is injected or rubbed on, make sure that whomever performs your treatment does not get too close to your anal sphincter, or you may be in a messy situation, how long?...it "Depends!" Good luck and be well.
Web reference: http://www.blippitt.com/that-would-be-in-the-butt-bob-video/