I am slightly confused with the Workday function and would appreciate advice.
If I have paid someone to work 21 days (Monday to Fridays, weekends
(Saturday and Sunday) excluded, starting work on 1st February 2010 then I
would expect their last working day to be 1st March 2010.

Using the Workday function (not including holidays) then I get an answer of
2nd March 2010. As below
=WORKDAY(DATE(2010,2,1),21)

To get my required date then I have to put -1 at the end. Is this correct?

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with kind regards

Spike