Does Sage support ODBC? IF so, that would seem the logical option to use here.
IF not, what file formats does Sage support for importing data? If you can determine the file types and data formats that Sage can import, you should be able to set up a system where you export data to one of about a half dozen different filetypes with the dat formatted the way Sage needs it to be and then you will need to import the data into Sage. If this is a windows system, if you can figure out command lines that will make Sage correctly import the data, you can perform those command lines via a script in FileMaker.