Can we block some users from the same domain to send mail to particular group in that domain

[somashekar M C]

I am using postfix with amavisd-new and i am new to mail server.
I don't know i am asking a silly question or not... but pls help.
Is there a way to block some users from the same domain to send mails to
particular group with in that domain.
Example: I don't want a...@example.com, b...@example.com send mails to
gro...@example.com, but I want
c...@example.com or d...@example.com..etc can be able to send mails to
gro...@example.com. Is it possible?
If possible let me know how to do that.