folders that can't run programs

is there a way that you can make a folder, and all of its subfolders, not be able to run programs from i.e. make it so you can't run a program from your desktop? My son is always downloading new programs on our home mac and i'm afraid that he is going to accidently download some spywear some day so i want to make it so that the folders under his managed account can't run programs so that the only programs he can run are the ones in the aplication folder.
Thanks in advance!

The are various parental controls available in system preferences > Accounts that might help. Pulling the plug on the Mac until he shapes up is another.
Best.

thanks! That was just what i was looking for.