Emulate RightArrow GUI Event

I'm working on a project where I need to navigate a GUI textfield (move cursor left, right, up, down) through a special input device (in other words, without access to the arrow keys).

This is the basic idea - it works fine for regular letters (a, b, c, etc) but not with anything non-alphanumeric.

 var e : Event = new Event();
 e.type = EventType.keyDown;
 e.keyCode = KeyCode.RightArrow;
 Event.current = e;

It looks like the "functionKey" propery of Event might be to blame - it might work if that was true but it's read-only...