Here is how I propose it.
You start an non-secured intermediary database that will capture your
Windows username.
In this db, you have a table already populated with your username and a
less-than-useful password in this case. See
http://www.mvps.org/access/api/api0008.htm
You can use the hide property of this table, preventing it to be noticed
from the list of tables
From that db, you call the secured db with a dos command line with switches
/user and /pwd
Of course, the security is far from perfect, but typically very few users
have the knowledge to crack it.