[Ti] MacBooks - why the lack of a built in scroll ball?

[Ardeshir Mehta]

On 16-Jan-06, at 8:38 AM, John Azevedo wrote:

> On Jan 10, 2006, at 10:07 PM, Ardeshir Mehta wrote:
>
>> Uh ... just a minor rant: Why don't the MacBooks come with a built- 
>> in scroll ball at the top of the trackpad, *à la* Mighty Mouse?
>
> Have you tried two finger scrolling on the track pad?

Unfortunately my TiBook (bought in July 2003) can't do it. In fact  
till recently I didn't even know it was possible!

Can I retrofit my TiBook to do it?