Increasing number of textboxes in a form on demand

I am creating a set of latitude and longitude textfields for a node creation input form. Some nodes may only have 1 set of lat/long coordinates, while others could have multiple sets.

I have seen forms (CCK modules) where the form is initially built with 1 text field with a "more values" button below that will add another text field when the users clicks it. I have done some research on Drupal, however, no matter what wording I use I end up with completely unrelated issues. Does anyone know of a page containing information on this subject? Any help is greatly appreciated.