Query and upload to Comments fields

Hello.  We are are making multiple distribution adjustments to change the accounting unit and activity/account category for a major project.  To provide a cleaner audit trail, we would like to add a standard comment indicating the change was made for this project and a reference for further documentation.

Is it possible to upload to the AP Distribution or Invoice Comments fields?  And is it possible to query them?

Thank you,
Sherry Shimek