On a more serious note, text field, deferUpdates and rejectUpdatesWhileFocused off. Value change event that fires on browser source only, that applies regex filter to entered value and strips unallowed items (\D if using java regex) or enters the max/min value if going beyond edges and writes it back to a custom property on the view. The numeric entry is bound unidirectionally to this custom property.
I think you could also use this script to send focus to the next box on 3rd digit entry.
Might still be racey or loop inducing.