Are you looking to force scanner input instead of allowing keyed entry? You can set up a script that has a Key Capture for each keystroke value and then chose to selectively ignore those keystrokes by doing nothing with the input.
What Matt said or you can ESC the keyboard to disable with a script as well.
Script( KeyBoardOFF )
Activate( From_Menu )
Keyboard_Disable( TRUE )
and FALSE for on