VBA macro for splitting automatically very large DOCX files

We have large DOCX files over 10 MB that we want into split completely independent single DOCX files.

We need a concise WORD macro snippet (SUB) that should do this.

1- Running the macro in WORD should split the file at locations in the file where we could add a certain SIGN/TAG.
2- The macro should save then the split DOCX files in the same folder destination as the main DOCX.
3- The name of each file should be automatically set, when saved, to a 13 digit number given next to that SIGN.
4- The macro should work perfectly on our site, and all instructions well communicated how to apply it.

Alternative suggestions for solutions are welcome.

Please indicate in your offer your experience with MS WORD, VBA MACROS.

Follow up is possible if project well done.

Look forward to your offers