manytomany field and intermediary table from a legacy database

I know that when I define a manytomany field automagically "behind the scene Django creates an intermediary join table to represent the many-to-many relationship".

Now I have a legacy MySQL db, feeded by an existing procedure built in Filemaker  via ODBC, which I would like to use with django too. In this legacy db the "intermediary join table" already exists but with a different name and with different name fields.

How can I tell Django to use that table without creating a new one?

An example would be very useful.

Bye from Rome

Vittorio