Something has to "serialize" the process.  This can be by
explicit agreement as to whom, what, where, when, and/or how;
or a computer process that only allows one of the list-owners
to signon to (whatever) at a time.
 
This subject has been discussed many times and there are
a variety of answers already provided that might be just
what you need.  Therefore, I suggest some searches of the
LSTOWN-L archives for various discriminators e.g.,
 
SEARCH MULTIPLE OWNER IN LSTOWN-L
 
as a first pass.
 
--  co-owner:   INFOSYS, TQM-L, CPARK-L, ERAPPA-L, JANITORS, LDBASE-L, et -L
URL:mailto:[log in to unmask]                "I get paid by the millisecond"