Using Outlook 2003 or later, is there any way to craft a link on a webpage
that Outlook will process by opening a new journal entry and populating the
subject line?

The goal is to have something similar to:

?subject="this is a test"

only with a journal entry.

A link that calls Outlook with the /c ipm.activity switch will open the
journal entry but I don't see any way to pass along an argument to populate
the subject line.