Multi-file checksum comparison

I often will split large files into multiple files to store on FAT-type drives and would like a way to find the checksum of a group of split files as if they were the original 4+GB files. With that, I'd like to create a button where i could select some files and have it calculate the checksum as if (for example) 4x4GB (or however many) files were one continuous 16GB filestream. Is there a way to do this and have the result pop up as a readable (copyable) messagebox or other type of dialog? This may also be useful for me to compare the original large file with the splitted multiple files.

Thanks for any help you may be able to offer.

Using a multi-volume archive to store the files might be a better idea, since e.g. 7-zip archives will tell you the checksums of the files inside them (and also let you test that the data is not corrupt).

If you want to keep using raw split files, there isn't a built-in way to run a checksum across multiple files as if they were a single file. You would have to use an external tool (which Opus could automate), or temporarily join all the files together (which would probably be slow), or write a script to do it (i.e. implement the checksum algorithm in a script).