changing key bindings in visual-block state only

Is it possible to change settings only in visual-block state but not in visual state? I want to remap a key binding only in visual-block state, and there seems not to be a hook for this specific purpose, though there are hooks for entering and exiting visual state. Also, what's the difference between normal state and motion state? I've tried various commands in both modes and they seem to do the same things.