In my day, we had to walk 20 miles in the snow to get to our neighbor's lawn and mow it for merely $0.01. Then, we had to be back by sundown so the wolves wouldn't get us.
Just password the file to Blockland or something, but it's his computer. If you want him to stop playing,
A. kill him
A. Get a new computer
A. Give him AIDS
A. Get him or yourself a key
B. Ask him to stop
or
C. Any comments in other posts.
Remember: There are things more important then Blockland. If your not willing to work or compromise for it, then don't bother with it.