It can't be done unless the databases are identical copies of each other - otherwise the LSNs in the databases get out of sync. It's an often-requested feature of SQL Server that may come in a future release.
Paul Randal
CEO, SQLskills.com: Check out SQLskills online training!
Blog:www.SQLskills.com/blogs/paul Twitter: @PaulRandal
SQL MVP, Microsoft RD, Contributing Editor of TechNet Magazine
Author of DBCC CHECKDB/repair (and other Storage Engine) code of SQL Server 2005