Only with bibliographic management software, e.g. Endnote or Reference
Manager.
You could somewhat duplicate the idea by converting the existing footnotes
to endnotes, which would give you a list at the end. That *isn't* a
bibliography, but you could pretend it was one. Then manually find any
duplicates and replace those footnotes with cross-references to the first
time the source was used, being sure to update the pages numbers. The end
result might not be very correct or professional, but might work for you.
However, might be just as fast to copy and paste the footnote references
into a separate bibliography, which is more correct (be sure to adapt
punctuation).
Help will tell you how to convert notes and insert cross-references.
DM
