Typically, when you go to your Settings screen and search for wireless networks, you should get a list of networks available. There, if you click on your office wireless, NC SHOULD prompt you with the 'login' page as a dialog window. I have tried in this in a few scenarios and it works well (from a hotel, from an office). If it does not popup the window, maybe it's because it's not able to figure out the redirect rules.
Just so you won't feel so alone I have the same problem with the open wireless network at work. It redirects to an internal IP and I cannot connect. I also tried it with my android phone and it too will not connect. Post here if you figure out a solution.