Joining arguments o locate a page object

Code:

1 row for a product (1 selected) in a shopping cart is identified by the data below (the row has 2 fields - product and Quanitity)

<td class="productListing-data" valign="top" align="center">
<input name="cart_quantity[]" value="1" size="4" type="text">
<input name="products_id[]" value="767" type="hidden">
</td>


a second row for another product (2 selected) is identified by the data below

<td class="productListing-data" valign="top" align="center">
<input name="cart_quantity[]" value="2" size="4" type="text">
<input name="products_id[]" value="1271" type="hidden">
</td>

Hi. I'm new to working with Selenium IDE.

I'm currently automating some user journeys through an online sales portal. Once you've added 2 products to your basket and go to the checkout you see 2 rows on the UI

I want to be able to uniquely identify the 'Quantity' field for each row so I can check it's correct but this field has the same name on each row and doesn't seem to have a unique ID. Therefore it seems I need to link the quantity field to the associated product ID field for a unique identifier..........does anyone have any idea how I might do this?

Many thanks
Rob