Setting docx custom properties at generation time

[alainPannetier]

I'm trying to find a way to set MS word custom properties at report generation time.

My cover page template (docx) contains some references to MS word custom properties.
Ideally, at generation time, the corresponding values get extracted from the repository (path/selectors/sql) and inserted into the document (as custom properties). Then the document is "refreshed" to take the values into account.
I'm using EA 12.
If this is not available OOTB, I'm OK to script this but this would need to run on wintel, osx/crossover, Linux/crossover platforms so I'm looking for some "light" solution (by which I mean I'd prefer to avoid heavy SDKs - openxml/poi etc...).