Saving from Word - Custom Validation

Hello,

We're currently using SPO with the custom (canvas app) forms for validation, which work great within the context of a doc lib.

However, when saving from Word, the property panel appears and the various fields can be filled in prior to saving to a site. Is there anyway to do some kind of backend custom validation (api call, etc.) from within Word/Excel when saving to SPO, so that references can be validated to avoid a long list of files that need attention?

Hope the above makes sense and appreciate any advice.

Thanks,

Paul