Doing it using VBScript (or JScript) running inside Opus would be best, since then you can avoid DOousRT.exe.
(Running the commands via DOpusRT.exe would work, but it's asynchronous, so if there are a lot of files you might run into problems if too many commands get queued up or are running in parallel. On the other hand, scripts inside Opus can run commands synchronously.)
If you click the "Opus Manual" menu at the top right of the forum, it has links to the pages about scripting in the middle. The Command object is what lets you run Opus commands.
The first post here has what is probably a good example, where it updates the Focal Length field on files: