update form text_field on collection_select selection

I have form and a collection_select control. I would like to update
form fields (text box) when I select an item from the collection_select
box.

It's like selecting template from the collection_select and the template
automatically loads to text boxes.

Any help?

You will either have to use javascript or ajax for this. If you don't
know about them then start with google.

Colin