Carpetsmoker, do you mean
as described in this section of the man page,
Code:
If the second word of savehist is set to `merge', the history list is merged with the existing history file instead of replacing it (if there is one) and sorted by time stamp. (+) Merging is intended for an environment like the X Window System with several shells in simultaneous use. Currently it succeeds only when theshells quit nicely one after another.
as per you sig?
Sigh, I get so sore kicking myself for not finding those things by myself.
Thanks. It works.