Bulk Discount for quantity of different products, but same custom variant

[mavrosxristoforos]

Hello everybody!

Here's what we are trying to accomplish. Assume we have a shop with t-shirts.
We would like to apply a fixed amount discount when a user adds a specific quantity of specific size t-shirts.

When I say specific size, I mean we have a custom string field with sizes: S;M;L;XL.
We add this custom field to some products (some may not have all sizes).

What we want, is that when a user adds two SMALL sized t-shirts, we would like to have a 25 euro discount. If they add 3 SMALL sized t-shirts, we would like a 50 euro discount, etc.
We wouldn't want a discount if the user adds two different sized t-shirts.

The sizes are not child products. They are just different values of a single custom field (set as adminlist).

Is there any extension, or perhaps an option or even a hack that we could use to achieve this?
Even a smal hint may help.
Thank you in advance!

[Jörgen]

You could check awocoupon. This extension can create very complicated discounts.
I think istraxx has a quantity baed discount plugin, not sure if it is applicable, check with max at istraxx.

Jörgen