You mean to associate single Apache Vhost to multiple WAS applications or multiple WAS servers.
Assocation to Multiple applications: No tricks involved as long as each application has seperate context-root and WAS plugin will redirect req appropriately.
Assocation to Multiple app servers: As long as these multiple app servers are part of "clustered group" you can do it. From WAS server side create a group plug-in file and copy it over to Apache VS.
If app servers are not clustered a single Apache VS cannot assocate to both. you might actually need seperate Apache VHosts or seperate Apache instances
Thanks
Sudhir Nallagangu