The DAISY XML file can then be processed to produce digital audio and other formats.
The plug-in is expected to be available in early 2008.
Microsoft is campaigning to have its Open XML document format approved as an international standard, which would help it gain wider adoption by public-sector organizations.
It failed to capture the necessary majority in a September vote by members of the International Organisation for Standardisation (ISO), partly due to concerns the format is not truly open but rather a ploy to lock in users.
An ISO group will meet again in February to try to agree a consensus.