[exim] Simple if-else condition in acl_check_rcpt

Hello,
I have some problems with spamers.
I have found the following
http://www.sant-media.co.uk/2010/03/how-to-configure-exim-to-receive-email-for-domain-only-from-specific-ip-addresses/

but this I want to use only for a certain domain.

I need some help so say the following in exim syntax:

# list of IP's
hostlist filter_relays = net-lsearch;/etc/filterrelays :
net-lsearch;/etc/relayhosts
# list of domains
domainlist filter_domains = lsearch;/etc/filterdomains

if $domain is in $domainlist
   deny
       !hosts = +filter_relays
        message = Your IP $sender_host_address is not allowed to send
mail for $domain