I don't know about limiting bandwidth for a single user, but you can certainly limit access time, or prevent access by one computer completely.
You should be able to configure the Access Control settings in your dir-655 router to do what you want. Look through the router manual for help with that: http://www.dlink.com/products/?pid=DIR-655&tab=3
Looks like certain kinds of browsing (streaming, online gaming, etc) gets assigned higher priority by your router. So, limiting the access time might be more likely than somehow limiting bandwidth.