I thought I'd post this here for anyone trying for the 100 trainer challenge in the castle courtyard and can't get what they want.
First off, this will NOT work 100% of the time, the bigger area you are aiming, the more likely it is to happen.
Here is what I do:
When the wheel starts, move the pointer to the top of the wheel and move a little to the left, to the end of what the first stats is would be a nice place. Focus on what you want done to your pokemon and start the wheel. When the end of the wheel gets on about 5:00 on an average clock, shoot! With proper timing, you will land on, or get VERY close to the thing you wanted on the wheel. This works a lot for me and helps me get out of frustrating spots, like wanting a stats heal instead of PP restore.