You can use the numbers counter in after effects. You just have to stop thinking one layer. the other option is to use expressions. But as I remember you are on after effects 4.1. All you have to do is a little masking and set up your hundreds or thousands or tens place as a single layer. And just animate each of the segments of your number.
Thanks for the reply. I'm actually workin on AE CS5 at the moment, if that changes anything?
I came to the same conclusion as you - to break down the whole number into seperate clusters. The problem I'm finding at the moment is that if I set the Type as "Number", and enter a starting number, playing with the timeline slider doesn't change that figure. Any idea what I'm doing wrong?
I should say that I'm very new to AE, so handle me with kid gloves!