>As they claimed to check date fields at runtime (ie EXE) for which source is not available, is it possible by using display memory to tempfile,
>and then checking accordingly?
>
>and then using SET LIB command and LOAD etc ?
>
>Is that what they are doing ?

I suspect they've intercepted all of Fox's date handling bits of code - the TSR might detect Fox's start up and then modifies the code sequences in memory. Who knows?
They claim to check memvar's as well (of course).