Marking Golf Ball before all players reach green

Question
I know from courtesy, you mark your ball on the green. Is there any rule specifying having to mark, or not having to mark, or when do you mark. Situation: 2 players 20 yds off green. Player A hits ball to green. Does he have to go mark ball, or can Player B request he not mark ball, no matter where ball lies? Player B says to time consuming for A to mark ball while he waits.

Answer
Chuck,
Great question! I checked out the USGA and could not find any rule pertaining to marking the ball when approaching the green. However when putting or intentionally putting the ball in the way when putting has rules. So hit away. Just remember if your ball is hit you are putting from where it ends up not where it originally landed.
Recall the hole in one on a par three a week ago. The second golfer hit a shot the landed, hit the other golfers ball and boink! in the cup!!! The other guy was putting a little further from the hole.
In golf history it used to be part of the game to "stimey" the golfer by getting in the way as a strategic way to even a hole.  

Thanks Again
Jim
International clubmaker of the year
www.mcgolf.net