Check and uncheck checkboxes

I want that - when people tick a checkbox for Delete in a form - that a confirm screen pops up to verify their choice.
I begin by testing with confirm() and if it's 'true' then check the box they chose.
If not true, then uncheck the box they chose.

How do you UNcheck a checkbox box?

Code:
<BLOCKQUOTE><font size="1" face="Verdana,Arial,Helvetica">code:</font><HR><pre><script language="JavaScript">
<!--
function Delmsg(productID,product_description,fieldname) {
var msg;
msg = "---------------------------------------- Caution message --------------------------------------------nnn";
msg += "Are you sure you want to delete this one?nnproductID:tt ";
msg += productID;
msg += "nproduct_description:t";
msg += product_description;
msg += "nnn---------------------------------------- Caution message -------------------------------------------n";

if (confirm(msg)) {
document.change_product.fieldname.checked;
} else {
!document.change_product.fieldname.checked;
}
//alert(msg);
}
-->
</script>[/code]

Call:
<BLOCKQUOTE><font size="1" face="Verdana,Arial,Helvetica">code:</font><HR><pre><input type=checkbox name=delete_0 value="500NO" onClick="javascript elmsg('500NO','Single Computer, 500K','delete_0')">[/code]

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¬ peterbe.com ¬

Found it!

<BLOCKQUOTE><font size="1" face="Verdana,Arial,Helvetica">code:</font><HR><pre>
<script>
var box;
box = eval("document.change_product."+fieldname);

if (box.checked != true) {
box.checked = false;
} else {
if (!confirm(msg)) {
box.checked = false;
}
}</script>
[/code]

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¬ peterbe.com ¬