There is a straight forward method for changing Chicago A in EndNote to accomplish what you want which is described in this post - http://community.thomsonreuters.com/ts/board/message?board.id=en-files&message.id=197&query.id=19522#M197. This method would provide the complete footnote and remove the bibliography so no modification would be needed after a reformat and you could re-use the style for all appropriate future publications.
So we can create a modified style for you and coordinate with your EndNote Web site admin to get it posted if you provide your institution information. (Note: Often the site administrator will make these customizations for you.) You can do it directly with EndNote and we can put you in touch with your admin to get it posted. Lastly, we can investigate the frequency of this request to provide a standard Chicago A footnote without a bibliography.
Let me know your preference, specifically if you would like us to coordinate getting the style posted through your administrator. The goal of our applications is to make formatting easier, and I believe we can still accomplish that for you.
Best regards,
- Mathilda, the EndNote Web team