Send Data from windows form to website's pop up windows

Question

I'm using vs 2010 & i'm working on windows form in which I've 2 text boxes, 1 button, 1 web browser control & i want whenever i click on that button, the data that entered in 2 text boxes should be transferred to the website's pop up window like i want enter data on 192.168.1.1 its username & password fields & should check whether entered data is correct or not. How can i get the name of that pop up window ? how can i do that ? 
Sorry for my bad english