Working with working days
Calculate working days between two dates
By Neale Blackwood
If you do calculations to work out completion dates with start dates and working days you should check out the WORKDAY function which ignores weekends and can also ignore public holidays if you use a list of holiday dates in the function. Check out the help system to see how the WORKDAY function can be used.
Also check out the NETWORKDAYS function which can tell you how many workdays between two dates. This also handles holidays if you include them.