Text Countdown

I want create a text countdown control that counts text down as its typed in a textbox or textarea

how do i go about doing this using c#

Not sure C# is really the way to go with this, Javascript is probably a better choice.

Here's an example I found by Googling:

http://www.smartwebby.com/DHTML/textbox_characters_counter.asp

C# example

http://www.rosshawkins.net/rfh/articles/asp.net-text-counter.html

That's a combination of c# and JavaScript - rather than one or t'other