An ARD description is obtained from the environment using the
supplied parameter name and stored in a group identified by the
returned value of IGRP2. If the last character in the ARD
description is a minus sign ("-") then the parameter value is
then cancelled and further ARD descriptions are obtained and
appended to the returned group. This process continues until an
ARD description is supplied which does not end with a minus
sign, or a null value is supplied.
If a GRP identifier for an existing group is supplied for IGRP1
then the group will be used as the basis for any modification
elements contained within the ARD descriptions obtained from the
environment. No checks are made for modification elements if the
symbolic constant GRP__NOID is supplied for IGRP1.