How to pass Username/password to Web Access page

We do not want to include the entire vWorkspace Web Access frame in the initial web page that our users connect to (the 600px by 400px box with the five tabs along the top).  Instead, there are two small login fields (username and password) incorporated in our existing page that, when submitted, pass the credentials to the familiar Web Access default.aspx, which shows users the applications they have access to.  It should be a fairly straightforward modification, but I'm not having any success.  Anyone have an experience doing this?

Thanks,

Sean