[thelist] DropDown boxes

I have 3 boxes,
one with countrie, the other with counties and the last with towns.

Ive been trying to find a fast effective way to change the content on the
drop down boxes depending on what country they pick etc..

So if they pick England, then all Counties in England would be displayed in
the second drop down box.

Hence if the select say Suffolk from the Counties drop down box then the
last drop down bpx would only show towns in Suffolk.

All 3 dropdown boxes are on the same page.
I'm using ASP to do this.
Or javascript.

cheers

paul