Thank you for your post.
If the Container field is in another table, you may want to consider using the script step: Go to Related Record
Once you are in the Related Record, you can use the script step:
Export Field Contents
In the Output File Path List above, you must set up a valid path first before using a variable. Also, be sure to check the option "Automatically open file".
It may be easier to post the script you have now, along with what barriers you are encountering when the script executes.