Sorry, last I checked, there is no sender-based routing support in sendmail. You cannot even try to create rulesets to get that.
Looks like it is my turn to eat humble pie. You will need to rebuild sendmail.cf after applying this hack.
http://www.cs.niu.edu/~rickert/cf/hack/sender_based_routing.m4
I have not tested it let alone tried on 8.14.x
I cannot believe the file is dated 2004. Ah well, I got rid of sendmail and replaced it with postfix in 2003 while I was still a mail admin. I must bow to the real sendmail bigots.