Environmental variable holding location of extproc.ora

Hi All,
We are migrating from 10g to 11.2 and trying to move from extproc configuration in listener.ora to extproc.ora<br/><br/>We are having 20 instances divided into 5 groups, each group uses different listener. Each listener has to have different ENVS for extproc.<br/>As we understood to keep it that way we would have to keep 5 different extproc.ora and somehow point instance to good use right extproc.ora during its start.<br/><br/>Is it possible? Does variable similar to TNS_ADMIN for listener.ora exists for extproc.ora?<br/><br/>Regards,<br/>Mateusz<br/> <br/><br/>