condition for calculating days

I have a following situation 

• I have one field that represents Project start date
• During projects I have a field that sums up all delays during the project (start of delay-end of delay) - one project can have many delays relationship
• With this I have project duration that gives me how long does the project last - total delay duration

Now I've inserted field PILOT DATE (date when we've started with the pilot)
The problem is when I want to calculate TIME TO PILOT (time from the start of the project to pilot date minus delays in between)

Is there a way to enter a condition to give me only delay duration up until PILOT DATE, and exclude all delays after the pilot date?