Of course it's possible -- you already did it -- unless I misunderstood you and you didn't?

chmod 000 /usr/bin/man to disable all permissions on /usr/bin/man .
UNIX file permissions are kind of the opposite of windows ones... on windows you might set a file 'read only', on UNIX a file must be set 'allow read' for people to read it in the first place. 0 means no permissions, 1 means execute, 2 means write, 4 means read, and you can sum those together to get combinations.

These are repeated three times, one for users, once for user groups, and once for world permissions, hence chmod 000 instead of just chmod 0.

To learn more about chmod, and UNIX file permissions in general, run 'man chmod'. Oh wait. First run 'chmod 2551 /usr/bin/man' to set man back to normal, then run 'man chmod'. The 2 in front is a special extra bit to allow others to run it as a different user.

---------- Post updated at 12:16 PM ---------- Previous update was at 11:34 AM ----------

Rereading the thread you still seem to be hunting for some magical "other" way to disable a program. There's lots of ways to do it -- overwrite it with a shell script that yells at the user, play tricks with mount to display an entirely different partition on /usr/bin/, set the noexec flag in your fstab so no programs in there can be run at all, alias 'man' to 'fortune' in your .bashrc, etc, etc, etc, etc, etc. Other admins could probably think of more creative and even sillier ways than mine. But none of these are the "disable_programs_without_chmod.exe" you think we're hiding from you. They're ordinary features for completely different things being (ab)used creatively. File ownership and permissions are the real way to get what you want done.