I have seen OpenUpgrade, which seems to be a utility to migrate databases between major versions of Odoo.  Is there any way to update a database schema when something changes between nightly builds?

Here's some background:  see this post, in which I described how creating a new database after updating Odoo allowed me to install my module which overrides the purchase order report body template.  The problem I have now is that we have another database that we need to update, but the Odoo backup/restore mechanism doesn't allow for the database schema to be upgraded.  When you restore the backup, you're still stuck with the database as it was at the time of backup.  Something changed in Odoo, but you can only use the changes if you create a brand new database.  Any hints?