I am trying to set up a percentage discount that will apply to item X if the quantity of X purchased is > 100.
It doesn't work to take the percentage off of the entire order because if other items are included they will also be discounted.
It also doesn't seem to work to discount the product price. The issue is that, if I set the quantity (to discount) at 100 it only discounts the first 100 items (i need it to give the same discount if 150 items are purchased) and if I set the quantity higher it gives a discount as if that number were purchased.

Am I missing something obvious?

thanks