problems calculating subtotal for order with discounts

["kenshin" <kenshin@planetanime.com>]

It's been a really long night and any help on this would be REALLY
appreciated.

I've been over and over the docs and it keeps getting more and more
confusing.

The problem i'm trying to solve is this:
i'm setting a discount based on a code like this:
[item-list]
          [discount code="[item-code]"]
          return ($s - [item-field sale_price]) if q{[item-field sale]} ==
1;
          [/discount]
[/item-list]

this all works fine, but using the [subtotal] tag i get only 1 item
discounted if there are multiple quantities ordered of the same product
code.  e.g.

                 regular price: 29.99
quantity 1 ----- subtotal: 24.00
quantity 2 ----- subtotal: 53.99
quantity 3 ----- subtotal: 83.98
etc.

I know there must be a simple solution to this that i'm overlooking but i
can't seem to find it.

Any and all help is appreciated.

Thank you
mike k.