Conceptually not too difficult. used the information in the post about file formats as a lookup. Had a few issues with running my batch macro. I think because I lacked a tool following it, it was only running for the initial record to save disk space. Either way when I put tools to follow it (browse then the tools to sum the value fields) it took a while to run but seemingly calculated correctly.
Was getting one row only after the macro/getting the ended on a downstream tool message. Came across this message for the first time and found it's resolved by putting a browse after it so good to know this!