Environment Variables in xdodelivery.cfg

I've been working on setting up an xdodelivery.cfg for Advanced Collections in 12.1.2. We are able to send documents to the printers without an issue. But we need to establish a temp directory for the cfg file:

<properties>

  <property name="ds-temp-dir">$COMMON_TOP/temp/</property>

  <property name="ds-buffering">true</property>

</properties>   

</config>

I'm having issues in getting environment variables to work here. Is there a way to make this work using environment variables? I also tried $[COMMON_TOP]/temp/ but no luck there. Unfortunately, hard coding the directory isn't an option for me.

Any help would be appreciated!

Thanks!

Chris