Production and Delivery Formula

Since I'm assuming you don't already have a worksheet available to work on, I attached an example that could be a possibility. Note that there are named ranges and data validation lists being used on the second sheet.

Cells C2:C4 are variable. You pick the first two from a dropdown, and enter the "Called On" date in the third cell, and cell C6 calculates the day that it is due (taking into account non-working weekends only). The formula has been made scalable by referencing data on sheet 2, so if your delivery dates or build day times ever change, you can alter them on the second sheet's tables and the formula on sheet 1 will automatically update.

Hope something like this helps!