[Exim] Multiple mysql connections (not just backup)?

Is it possible to have multiple mysql connections?

I have mysql setup in master->slave replication, but I would like to
write to db from time to time.

hide mysql_servers =
readonlyslave.mysql.com/accounts/readonly/readpasswd :
readonlyslave2.mysql.com/accounts/readonly/readpasswd :
readonlyslave3.mysql.com/accounts/readonly/readpasswd

Any way to do something like the following?

hide mysql2_servers =
master.mysql.com/accounts/readwrite/readwritepasswd

${lookup mysql2 { insert into } }

Lanny