Best way to incorporate a master list of codes into many different ind/indt files

I work in a highly regulated field with lots of beaurocracy. Each year, we submit templates to a regulatory body and receive an "approval code" for that year. We update these into our .indt file so that all net new work will have these codes. In this case, I have an .indt file with 8 parent pages of different fax templates, each with their own unique code (8 codes total).

Another consideration is that client work created from the now "old" template file needs to be updated as re-prints come up. It's on our very small team to catch this throughout the year (among a million other regulatory things). 

My current proccess is to manually copy and paste the codes from a list my co-worker makes. Not great.

I explored data merge as an option, but seems more tedious in some ways (manually adding placeholders to all client work, needing to click "preview" everytime i open the .indt file to see the codes). Is there a better way to have a "master list" of codes that can be easily implemented? Is there a script that can help?

Thanks!