a guest on Mar 19th, 2012 - pastebin.com/VxS6ZWqg

external.js

function set_new_material(materialObj) {
    alert(document.getElementById('paper_finish').value);
    document.getElementById('paper_finish').value = materialObj.finish;
}

main.html

<script src="external.js"></script>
<script>
var new_materials_screen = open(url, windowname, 'width=1200,height=800,scrollbars=yes,menubar=yes');
</script>

popup.html

<script src="external.js"></script>

<script>
var materialObj = {
    materialid: materialid,
    finish: finish,
    colour: colour,
    adhesive: adhesive,
    material: material,
    cost: cost,
    moq: moq,
    vendor_name: vendor_name,
    ring_for_price: ring_for_price,
    product_id: product_id,
    number_of_vendors: number_of_vendors
};
set_new_material(materialObj);
</script>