Interrupting JS function on keystroke

[The Devilish Cavalier]

Hi all,

I'm writing the online equivalent of a noticeboard using a really simplistic system of PHP, JS and HTML. A comment is added by an HTML form posting to a PHP page, which then appends the message to the text file containing all messages ($transcript.txt). The page this is on reloads every ten seconds using a JS function, but here's the rub. I can't use a frame (as far as I know) to display $transcript because of the height issues, so the form and the file are on the same page. This is inherently a problem because I can't figure out how to get this function to stop on keystroke, which it has to do, or else messages of more thsn about 10 characters aren't a viable option.
Despite looking into onkeypress() etc, I can't anything to work. As far as I know, this is more a syntax than concept problem, but all the same, it's really bugging me. Any help will be much appreciated.
Yours,
DevCav