wine users - Jun 2010 - changing windows variables in wine

Hello all,

  I am a mac user running Wine to run geochemistry program on my mac under OS X
10.5.8 using Wine 1.1.35. I've got two out of my three programs up and
running without a problem!

When I try to run PhreePlot I get the following error in the wine command
prompt:
***Error: Invalid PhreePlot system path.
Check that the PhreePlot environment variable is specifying a valid directory
(29).
PhreePlot system path = C:\users\ara\Application Data\beta\system\

I typed set at the dos prompt and found out that the variable is set to this:
PHREEPLOT=C:\users\ara\Application Data\beta\

Is there a quick way to change the variable? I've tried searching for
answers to changing variables but everything I found relates to installing wine
from scratch.

Thanks for you help!

Ara

http://www.winehq.org/docs/wineusr-guide/environment-variables

(When doning it from a *nix prompt, use single quotes, then you don't
neet to double all the slashes...)