var list = .... ;

list.lastKey = 0;

list.lastKeyTs = 0;

list.onkeyup = function (evx) {

var e = (evx? evx : window.event);

var k = (e.keyCode? e.keyCode : e.which);

this.lastKey = k;

this.lastKeyTs = (new Date()).getTime(); // timestamp

};

list.onchange = function () {

if (this.lastKey >= 33 && this.lastKey <= 40) {

var t = (new Date()).getTime();

if (t-this.lastKeyTs <250) return;

}

this.form.submit();

};