setlocale comma decimal question: GRACE and GMT

[Glen Snyder <gsnyder@rice.edu>]

I am using Debian sarge, and have two applications which I use to create
maps (GMT, Generic Mapping Tools) and plots (GRACE). The problem I have
is that a journal that I am submitting to requires the use of a comma
instead of a point for the decimal. The data I am inputting into the two
programs is in the form of xy and xyz data with decimal points, and I
only need the comma on the output (numbers on the axis, numbers in the
scale bar). 

I have addressed this question to the user groups at GMT and GRACE with
no response, so I thought maybe someone using Debian would have an
answer:

Does anyone have an example of a bash script that would use setlocale to
temporarily call on LC_NUMERIC to output comma decimals (and then switch
back to the dot for the decimals afterwards)?

Thank you in advance for your kind response,
Glen