target input by type and name (selector)

Question

You want a multiple attribute selector

$("input[type='checkbox'][name='ProductCode']").each(function(){ ...

or

$("input:checkbox[name='ProductCode']").each(function(){ ...

It would be better to use a CSS class to identify those that you want to select however as a lot of the modern browsers implement the document.getElementsByClassName method which will be used to select elements and be much faster than selecting by the name attribute

You can combine attribute selectors this way:

$("[attr1=val][attr2=val]")...

so that an element has to satisfy both conditions. Of course you can use this for more than two. Also, don't do [type=checkbox]. jQuery has a selector for that, namely :checkbox so the end result is:

$("input:checkbox[name=ProductCode]")...

Attribute selectors are slow however so the recommended approach is to use ID and class selectors where possible. You could change your markup to:

<input type="checkbox" class="ProductCode" name="ProductCode"value="396P4"> 
<input type="checkbox" class="ProductCode" name="ProductCode"value="401P4"> 
<input type="checkbox" class="ProductCode" name="ProductCode"value="F460129">

allowing you to use the much faster selector of:

$("input.ProductCode")...

input[type='checkbox', name='ProductCode']

That's the CSS way and I'm almost sure it will work in jQuery.