problem with promotionEngine.Evaluate() when using custom promotion.

Hi Team, 

 when I am trying to use evaluate method to display promotion detail in the product listing page.

My custom promotion logic: In my custom promotion filtered the line items based on the required quantity(line items should > than required qty)

My problem: I am using  PromotionEngine.Evaluate(contentLink...) method to find the product has a promotion or not. But as per our custom logic promotion is not applied to the products.

So based on the OrderGroup type(cart, InMemoryOrderGroup) can I skip my filter?

Is this the right way to do or else any suggestions are welcome.