An example of ENTRY_PROG:

1) Type: ENTRY_PROG
2) ARGS: 50
3) Commands:

The ENTRY_PROG is used whenever the mob moves.  If the mob
moves, it takes a look at ARGS.  It then makes a random roll,
and if the random roll is less than args, the command is
executed. (the random roll is between 0-100)
If you set ARGS at 100, the commands will automatically be
executed, when the mob moves.

If you don't know what ARGS is, read ARGS.