Load a page invisible and fetch a form value

[linearfusion]

I am creating a customized home page that can display regular links and login forms. I am adding Gmail login form into it. I can further customize it by putting multiple sign in buttons that can fill in username/password for different accounts before submitting.

Here's the preview:
http://imgur.com/s4Ert.jpg

Now the problem is, in Gmail login form a hidden variable called "dsh" is filled with a value that is matched with server as well as a cookie, this value changes in some hours. So this means that I cannot create a complete offline form, but is it possible to load the login page hidden, and catch the value from it?

I tried with an iframe with display:none and src="http://mail.google.com" but it opened in the top frame. Any other ideas?

In short, what we need is, every time a page is opened from my computer, an online page should be open invisible from the user, and a hidden form value is to be fetched from it.