If you want to define a sequence of environment variables in a job, where one variable references a previously assigned variable, e.g.
ORACLE_BASE=/u01/app/oracle
ORACLE_HOME=$ORACLE_BASE/product/10.2.0.3
there are two options.
If this affects a small number of jobs, you can create the variables as commands, see the first attachment.
If there are a lot of jobs, create a file as in the second attachment, and reference it in the job as in the third attachment.
This applies to *NIX. For Windows, for the first case you can follow a similar approach using
set A=value
set V=%A%added
and for the second case, you can create a .bat file that sets the required variables, then specify that in the job's command, ie
the file set_vars.bat contains
set A=value
set V=%A%added
and the job's commands are
set_vars.bat
first_command ...
and so on.