I noticed this post which is close to what I want, http://forum.gravityhelp.com/topic/hide-the-submit-button-conditionally, but not exactly. What I want to do is disable the submit button, not the data that is contained within the form.
The website is behind a firewall on an intranet, so I can't give you the link, but here is the source for the form.
Since there is no id for the the submit button, I am not sure how to do it.