mysql modifications

Hi, I need to add a foreign key to the radcheck table, but the tables are in MyISAM, and not InnoDB. When I tried changing the table type to InnoDB, I get back errors that the table cannot be created. Is there any way to add a foreign key into the tables created using the db_mysql.sql script found in /usr/share/doc/freeradius/examples? If not, are there any other ways to accomplish this? Thanks, Simon