How do I prevent my mac's wifi from ever (not just once) seeing a particular wifi network?

So here is my dilemma- I'm addicted to the interent and I don't want to have the option of using it in my home except for particular times. On my own network, I plan to change the password to something long and unmemorizable and write it down and leave it somewhere else (say the coffee shop) /tell it to a friend etc so that I can have the option of using it- then tell my key chain to forget the network's password. Problem solved! The only issue is that my upstairs neighbors have a network and I know the password! If only I could delete it from the keychain in my head, but I can't. I can ask them to change the password, and will, but it's not their problem and I feel silly doing so. Plus even if they do it'll take them forever.. So my question is is there a way to prevent my computer from using that particular network, forever- so that my computer sees it and automatically ignores it?

Any help much appreciated!