Fig 1: HTTP Redirect in IIS 7.0
"Redirect requests to this destination" text box can be used to specifyt the destination of the redirection. Once you specify the destination url click on "Apply" link in Actions pane to save the settings.
Apache web server is support to IP based redirection that allowed you to specify diffent IP for the diffirent website in the web server and DNS can redirect based on the IPs of the websites. But so far IIS web server doesn't support for this featrue. So that you might need to use this featrue to redirect your users to exact location.