Home Network Prank

I would like to play a HARMLESS prank on my twin-brother while he’s on his PC at the sametime I am though our home network. I am cabled in the router and he is using the WiFi as he is too far away for a cable. I just want to see where his mouse is, and move it all over the screen. (Ex: right when he wants to go left, etc).
I do not and will not install any software(s). Is there something I can do to make him laugh…He needs a good one lately…this is a good joke. Recently he did something simular to me…and won’t tell me how it was done! Revenge is so sweet! Maybe I can use an MSI or Hyperterminal? (We both have Windows XP).

Can anyone Seriously help me pull off this prank??? !!! ???

Please RSVP. Thank you!