instead of using a calculation for this, you would use a discount rule on the discounts tab.
Set the trigger to:
"Number Of Items with A Specific Column value"
if the number of items where "category" has a value of "category name" is ">=" a value of "3"
and in the calculations section, use:
"Based on items with a specific value"
Total of "Total Price" where "category" has a value of "category name" "times" "0.10"
I have set that up but it does not work how I want it to. I have set the rule to look at the VolumeDiscount column in eCart and then give 10% discount if there are 3 of more of the VolumeDiscount category in the cart. See attachment: rule.
This works fine, see attachment: invoice. Both items have the same VolumeDiscount and they total up to 3 and the discount is applied.
What I want to happen is that the discount is only applied if a single or multiple rows meets the rule so in the attachment: invoice if 43956 was set to quantity 3 and 79700 was set to 1 I would like the rule to work for row 43956 and apply 10%. Equally if both 43956 and 79700 where set to quantity 3 then the rule would apply discounts for both rows.
Maybe the rule has to calculate based in a unique ID and VolumeDiscount, only guessing here..
Hope you follow.