Well... here is a small info that will help you.
remember that the documentation says:
SO.... here is what to do.
1. when you add the entry in the DB make sure you add it in the middle of the table right after the "products_model"
2. now lets take a look at the categories.php.
do a search for the key word "products_model". (I found 10) ok?
now lets look at the first result you should see:
'products_model' => tep_db_prepare_input($HTTP_POST_VARS['products_model']),
(actually that code displys to results from our search)
SO WHAT TO DO YOU ASK? Well it is simple. just create the following line after it.
'products_upc' => tep_db_prepare_input($HTTP_POST_VARS['products_upc']),
3. lets move on to another example.
$product_query = tep_db_query("select pd.products_name, pd.products_description, pd.products_url, p.products_id, p.products_quantity, p.products_model, p.products_image, p.products_price, p.products_weight, p.products_date_added, p.products_last_modified, date_format(p.products_date_available, '%Y-%m-%d') as products_date_available, p.products_status, p.products_tax_class_id, p.manufacturers_id from " . TABLE_PRODUCTS . " p, " . TABLE_PRODUCTS_DESCRIPTION . " pd where p.products_id = '" . $HTTP_GET_VARS['pID'] . "' and p.products_id = pd.products_id and pd.language_id = '" . $languages_id . "'");
can you see where the products_model is? good just add after it "products_upc,"
Hope that will help someone.
Have fun