I was about to mark solved yesterday while I was writing this reply, but then I guess I got distracted by something and never hit "Post Quick Reply"...
While I was trying different things out yesterday I came accross "killall" which will do exactly what I want it to.
All that I needed to do is specify what is in the "Command Name" section of, for example the "ps -ef" command...
# killall -v "/usr/local/nagios/bin/nrpe"
Seems to do what I need... i.e. kill process based on the "command name".