My kid needs something to do....?

I have just started brining my 4 1/2 year old son to work with me. He has been here for about a week and is bored. I have converted the conference room into a playroom, with tv, dvd player, vcr, v-smile, building blocks, race cars and a bunch of other things for him to play with. We also go to the play ground near by during my lunch break, but he is still at my desk every 5 minutes saying he is bored. Can anyone give me any ideas of things he might be interested in doing??? I try to interact with him throughout the day, reading him a story or working with him on writing his letters, but he just has so much energy i can't do my work and keep up with him without going crazy. a babysitter is not an option right now.. so please don't say send him to a sitter.