Pause task for number of days by subtracting "scheduled ship date" from "scheduled arrival date"

We have a requirement of invoice pause till shipment is delivered to the customer. We cannot use the "scheduled arrival date" because actual shipment may vary from the "scheduled ship date" & accordingly "actual arrival date" will also vary. "Scheduled Arrival Date" will be populated from defined "transit time". So we are thinking to put a pause task which will be triggered immediately after the shipment task & will wait till the number of days needed for the transit & should be derived by subtracting "scheduled ship date" from "scheduled arrival date" in the pause rule.

Is this possible?