Filtering based on domain name

Hi

I am using sendmail as MTA and procmail as MDA. Now I have one user
whole(_at_)mydomain(_dot_)com which is forwarded to many users using .forward. 
I want
that only few selected domain can send mail to this address. Mail from
anywhere else will bounce back. How do I  implement this?

Any help will be appreciated.

Best Regards

Jayanta

Jayanta Mukherjee
Vedika Software                Ph   :91-33-2473810
5B Sarat Bose Road          Fax :91-33-2479474
Calcutta-20
India
http://www.fact.com.sg
http://www.allindia.com