Configuring a backup network

Several of our servers are dual homed. The second nic in each is on a
"backup" network. The purpose of this is to load ballance server to server
communication, leaving the primary network relatively free for the other
computers to use. I have done some research into how I could do this, and
have come to the conclusion of setting up weighted route statements that
prefer the backup network for server to server commuication. The only
examples of this that I can find refer to load ballancing two ISPs. To give
you a graphical view of what I am trying to do:


)
internet )--------+------------+--------------+
) | | |
[server1] [server2] [workstation1]
| |
+------------+

Any ideas on how to get this working?