AFAIK each Domino server instance can only have one Mail Journal location (local store or remote mail-in address). Probably not what you want to hear, but to achieve what you need I think you need to look into Partitioned Servers:
http://publib.boulder.ibm.com/infocenter/domhelp/v8r0/index.jsp?topic=%2Fcom.ibm.help.domino.admin85.doc%2FH_PARTITIONED_SERVERS_OVER.html