It sounds like you are confusing client-side technology and
server-side technology.
Coldfusion only deals with
server-side technology - mainly information that has been
submitted via a form or url request to the server. CF generates a
page and then presents it to the browser. CF doesn't really have
that much interaction with the data on the page until another
request comes in (i.e. after form submission, a link is clicked,
etc)
Client side technology such as JavaScript allows you to
interact with the contents of your page before the information has
been sent to the server. Your DOM example is obviously a JavaScript
address for a field on your form. Once you submit the form, CF will
have access to it in the FORM scope structure. Until then, however,
the only technology that can read/write to that DOM element is
client-side technologies such as JavaScript.
If you can explain a little more about what you are trying to
do, we can probably start you down the right path to figuring out
what you need to do.