Resetting And Restarting SetTimout() Within The Same Function?

I'm trying to set up an form validation through ajax and php. My goal is to have the php script called after the user stops typing, but without the need to exit the field (so, I don't want to use onChange or onBlur). I would like to use an "onKeypress" (or onKeyup/onKeydown) command with a delay (setTimout) of about a second or so. This way, the php script will not be called on every key stroke, but once the user pauses typing long enough for the setTimout to expire, and only then will it call the php script and perform the validation check.

Part of the script I'm having problems with is resetting the setTimout after each key stroke. I've got this much working:

Code:
<script>
function execute() {
setTimeout("validate()", 1000);
}

[Code]....

how to properly reset the timer after key strokes?