Greetings FreeRADIUS List

i have a special requirement, i need your help to understand FreeRADIUS virtual server(s) a little bit. i want to use FreeRADIUS for MAC authentication and i need the following results. 

if not found then accept the access
if found look for accept & reject value in the database table to send reply. 

My question is not that how to do it, but to know if do able. i shall read more documentation if possible to achieve. i would VERY grateful also, if someone can kindly send me the documentation link, which explain this kind of topic. 

Thanks / Regards
RM --