I have a puzzle I'm trying to solve. I am provided an end date to which I have predefined parameters for interim due dates (example: end date - 10 business days). I need to include a defined holiday table that will also factor into the calculation that also includes banking holidays. Is there another function I am overlooking? I am not very experienced with Excel programming.

END DATE MILESTONE1 MILESTONE2 MILESTONE3
12/31 -10 DAYS -13 DAYS -20 DAYS

Please and thank you for your assistance.