Using older confi files after yum update

Greetings!

I have been searching the web and the mailing lists for an answer to
this, but have been unable to find anything about it.

I have a config file that I have modified for my environment.  However,
when I do a yum update it overwrites this file.  I can restore the old
file from another machine and everything works fine.  Can I tell yum to
not replace that one file during a yum update?

Thanks!

Jake Adams