How to use an environment variable in the arguments field of a run/debug configuration?

(If I've missed it, please direct me to the appropriate part of the help.)

I'd like to know if it's possible to use an environment variable (one from the parent of a calling run/debug configuration) as part of the arguments field in a run/debug configuration. I've tried the (to my mind) naive approach of doing:

--argname $ENVVAR

The result was that the value passed was just '$ENVVAR', whereas I'd have liked the value of $ENVVAR to have been passed.

Is this simply not possible? Do I just need to learn the magic incantation?

Thanks!

Derrell