Need help with Javascript Assignment.

I want you to design a digital countdown timer on a page. Have a text field that accepts the amount of minutes to start at. Also include a button. Once the button is hit, throw up a digital clock like the following... 10:00 IE, show both minutes and seconds. Redraw this thing every second, until you get to 0 minutes and 0 seconds. As a hint, you'll be keeping track of the amount of time. You could try to keep track of both minutes and seconds, but I believe the easier solution will be to simply keep track of the amount of seconds, and do the proper conversions on that each second to get the display you want! This is a tough one! You can tackle it in a few ways, but I suggest a setlnterval call that pops every second