What subject are you in?
Are they journals or books (or book chapters).
How long is the document and how many citations/references are you talking about? Do you have access to a subject database (like PubMed?)
What is the output style that the bibliography was generated in?
Is there a way to reveal the Catvit field codes in the word document? If so, what do they look like?
Here are threads discussing convertion and some tools that are out there and some articles on how to convert a text document to an importable tagged document, you can look at.
http://community.thomsonreuters.com/t5/EndNote-How-To/Importing-FROM-Word/m-p/3996#M1311