Changing the environment of a running process

[Jan Willem Stumpel <jstumpel@planet.nl>]

In a few programs (e.g. Mozilla, Openoffice) I sometimes want to 
input European text, sometimes Japanese text. Omitting various 
details, this involves starting the program in a specific 
"environment", e.g.

    LANG=ja_JP mozilla

when I want to use Japanese in Mozilla.

For other languages, another instance of Mozilla has to be 
started, in which the LANG environment variable is set to, e.g., 
"en_US" (or just to the default, "C").

So I am jealous of MS Windows users who (if they have downloaded 
the appropriate stuff) have a little box on their screen which 
they can click on to switch the input from (e.g.) "Japanese" to
"English". In modern versions of MS Word, for instance, it is
no problem to input Japanese as well as several European
dialects (with accents, etc.) into the same document.

The key to doing something similar in Linux would seem to be the 
ability to change the "environment" of a running process on the 
fly. Is this possible, in principle?

P.S. There is a Debian package called xxkb which claims to switch 
the "keyboard state" between English and Russian. Does this go 
some way to providing the solution? The documentation is only in 
Russian, which I do not understand.

regards, Jan