Changing the Master Environment Variables

Hi!  I'm new to this group and came to ask a specific question.

Does anyone know (I'm sure someone does) of a way to change the master
environment variable and is anybody willing to help me on this subject?
I'm afraid I do not know much assembly and might have to ask someone to
write the complete function (not with main() but as a subfunction since it
will be a part of the program) for me (that is, all the parts that will
not be comprehensible without the knowledge of assembly).

I tried trying to figure this out by myself but I think that will take me
forever.  Thank you!

-Mark :)
MarkKKim@AOL.Com

PS: The format I need is TC++ 3.0
PPS: I do know some bits and pieces about assembly and approximately how
the memory is supposed to be configured but not enough to know anything
exact even such a small command as "pop"
PPPS: I'm a beginner C programmer