Rule to Apply Automatic Coupon with uc_coupon

Hello,

I'm trying to add a rule to apply a coupon when a certain number of a particular product is added, in order to give a discount.

I have a product where when four are added, I want a particular coupon to be added for a 25% discount.

So I created a rule. The event was: "After saving a new cart item"

My conditions are:

data comparison: uc-cart-item:nid = [product nid]
data comparison: uc-cart-item:qty = 4

Action: apply coupon

So I added four of this item, but the couponw as not applied. Any idea why this might be so?