If the app uses VFP ODBC driver there might be a chance of turing logs on. If the app is VFP natively accessing the vfp data, you couldn't even do network packet sniffing, the sql engine runs clientside and you only could log which portions of which files are read, if you can filter the packets sufficiently.
Are those reports standalone FRX files? Then you can probably see inside, what tables are accessed, if the dataenvironment of the frx are used.
Bye, Olaf.