creating sub-tiles of maps

[Dave Weaver]

Hi, 

I'm looking to create a web-based map-browser (of a similar style to Google
Maps etc) where the user only sees a small part of the overall map at any
one time,  and can scroll around it.  

I've just started looking into MapServer as a possible tool to help me
acheive this. 

So far I've run through the basic tutorials, and have created a small static
map, in a projection of my choice with an overlayed geographically-located
bitmap image. By changing values in the .map file (especially the extent) I
can zoom in and move around the map.  Not too difficult so far.

But what i'd really like is some way to serve sub-tiles of the map to a
javascript program, the size and location of the tiles depending on
parameters passed from the javascript. I have no idea how to achieve this
with MapServer. 

Can someone point me in the right direction? Which features of MapServer
will help me do what I want? What should I be looking for in the documentation?

Thanks,
Dave