Setting Revprops before Revision is Created

I know this sounds strange, but can you set a revision property before
a revision is created?

For example, I make some file changes, and want to mark that my
changes fixed bug # 1001. To do this, I'll set a revision property
"corp:bugbix" to "1001". Then, I'll check in my changes with the new
revision property.

There are several revision properties that are set before the revision
is committed: svn:log, svn:date, and svn:author. However, these are
special revision properties used by Subversion. I'd like to have a
pre-commit trigger to force users to set a particular custom revision
property before checking in their code.

I know older versions of Subversion could not do this, but I thought
1.5 or 1.6 could.

Just working on a new pre-commit trigger, and want to know if this is
something I can do.

-- 
David Weintraub
qazwart_at_gmail.com