Forum:Countdown Input box

Hi, Is it possible to create a input box with a starting value say 100. Then you put in a number say 12, then it takes 12 away from the current value (100) and updates say a subpage with the current value in? I'm thinking for my userpage on the Runescape Wiki... Just an Idea I had in mind. -- 18:19, September 12, 2009 (UTC)