[Greasemonkey] [Help]How to replace an js method or event?

[weide]

dear all,
When I visit a site in firefox,the onkeydown is not available,so I try
to write a js in greaseMonkey,but there is some problem.

The page's javascipt soure is this:
----------------------------

<script language=javascript>
document.onkeydown=nextpage
var prevpage="readchapter.asp?Bu_id=188758&bl_id=8334"
var nextpage="readchapter.asp?Bu_id=188788&bl_id=8334"
var bookpage="readbook.asp?bl_id=8334"
function nextpage() {
	if (event.keyCode==13) location=bookpage

	if (event.keyCode==37) location=prevpage

	if (event.keyCode==39) location=nextpage

}
</script>

----------------------------------------

And I write KeyNavigator.user.js like this:
---------------------------------
function NextPageForFireFox(e) {
if (navigator.appName=="Microsoft Internet Explorer") kcode = event.keyCode
else kCode = e.which ;

//alert(kCode);

if (kCode==13) location=bookpage

if (kCode==37) location=prevpage

if (kCode==39) location=nextpage

}

//window.addEventListener('onkeydown', NextPageForFireFox, true)
//document.onkeydown=NextPageForFireFox;
----------------------------------

But it do not work...,how should I do?



weide