mailscanner and perdomain white and blacklists

[Dave]

Hello,
    I've got a mailscanner install with sendmail. It's working fine and it's 
working for multiple users. Now i'm getting requests from user a to add a 
username/domain to a blacklist file and user b to add another 
username/domain to a whitelist file. These i'm thinking should be separate 
as they are separate domains. This is on an fc4 box. Is this doable, any 
help appreciated.
Thanks.
Dave.