window.onbeforeunload

If i'm using a script like this for a comment section:

<script>window.onbeforeunload = function() { return "Sure?"; }</script>

I don't want it to ask if they select the "add comment" button... it's basically a reminder for if they begin to navigate away without adding the comment.. any help would be greatly appreciated. Thanks.

Is it causing conflict because i already have an onClick event?

<input type='button' value='Clear' onClick="setval('CATEGORY',''); document.getElementById('CATNAME').innerHTML = '';">

here's the whole form if it will make it any clearer...

HTML Code:

---

<script>
window.onbeforeunload = function() {
    return 'Are you sure you want to navigate away from this page?';
};
</script>       


<div class='module_header'>New Comment | <a class='f' href='<?php echo matry::here_to('lookup'); ?>'>Cancel</a></div>
<form action='<?php echo matry::here(); ?>' id="rita" method='post' onchange="changes=true" onsubmit="var arr = new Array('NOTE1'); return mandatory(this, arr);">
<table class='edit'>
<tr><td>Note1 <?php tbox('NOTE1', 60, 4, 250); ?></td></tr>
<tr><td>Note2 <?php tbox('NOTE2', 60, 4, 250); ?></td></tr><tr><td /></tr>
<tr><td>Note3 <?php tbox('NDATA', 60, 6, 6000); ?></td></tr>
<tr><td><?php echo lookup_link('Category', 'category', 'CATEGORY=Category&CATNAME=Description'); ?> <?php inp('CATEGORY',2); ?>
        <input type='button' value='Clear' onClick="setval('CATEGORY',''); document.getElementById('CATNAME').innerHTML = '';">
        <span id='CATNAME'></span></td></tr>
<tr><td><?php echo button::save('Add Comment'); ?></td></tr>
</table>
</form>

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