Web page control, manipulation, javascript from c# windows app

I am writing a c# winforms application that needs to communicate with a web page. The communication needs and the problem is as follows:

1. How can i manipulate web elements such as textbox or input without loading or displaying the page in my windows application?
Adding a Forms.WebBrowser control and hiding it from view is the first trick that i can think.
2. Is it possible to invoke a javascript which can do the previous task (manipulating html controls) from c# windows app. ?
3. Maybe the hardest one: I need to detect which page the user is currently viewing in his browser so that i can accomplish the right manipulations on the right controls on the right web page?

Thanks.