Delivery Fee for Minimum "Per Delivery Value"

[NutriGreenFarms]

Hi,

I use seal subscriptions. My shop offers subscriptions and one time purchases for my products. I ONLY offer local Delivery to specific zip codes and I do not ship product. 

I have a $2 Delivery fee configured on orders < $15. The problem I am facing is that I have a 3 month and 6 month plan where the customer pre pays for the subscription. These values will obviously be > $15 and the delivery fee is not applying. I want to charge the $2 Delivery fee if their "Per Delivery Cost" is < $15 rather than the single order price. 

Is there a way to accomplish this?