Multiple select conditionals

Hi. I have a webform with a select list:

product1|Product 1
product2|Product 2
product3|Product 3

It is set to Multiple, so user can select more than one.

I then got another select list 'Quanity':

1|1
2|2
3|3
4|4
5|5

And I created a conditional and it works almost perfect, except... Since product select list is Multiple, when selected any multiple items, it would pull only a single Quantity field for all items selected. It makes no sense if you have only one quantity field for different items selected, it would work only as a total of all amounts, but how do you know quantity of each item? For that you need to pull separate Quantity field for each and every item selected in the product list.

...but how?