A good place to start would be Displaying Only Business Days
For holidays, I would start by looking at the logic in option 3 of Calculating Number of Weekdays Between Dates. Step 1 would be the same, but instead of subtracting the count of holidays, you would want to make a filter like [Date] != [Holiday Date]
If you run into issues, we are generally able to give more specific advice if you can include a workbook.
See instructions for creating a packaged workbook A quick method to anonymize a workbook is to hide any fields containing sensitive information before the data source is extracted. Hidden fields are not included in the final extract.
Hope this helps