Evaluate discount with visitor group

I have a Campaign with a Visitor Group applied and one or more Discounts under this Campaign.

I'd like to use the PromotionEngine's Evaluate() method to fetch the discount price of a product in this specific Campaign. I am trying to do this during a Scheduled Job in EPiServer.

However using the Evaluate() method returns nothing. I assume this is because that the job that is running the evaluation is not a part of the Visitor Group.

How would I go about evaluating the discount price of a product where a visitor group is applied?