As I mentioned before, it is possible to use Excel to create the missing feature of dynamic due dates for new projects. It can be done with simple math or better yet a decision to only include workdays. The =workday command is flexible in many ways and also can have a lookup holiday schedule table that you could put on another tab. Attached is an example with the logic to use the command or not. Everything feeds from the Project Start Date to the Task Start Date. If one does not have Start Dates then simply change the formula to work on Due Dates. Remember to keep both as a regular spreadsheet and CSV file for repeated use. The blue areas are your critical date inputs. Hope this helps.