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(WorkDate d, Numeric n)
Returns the date obtained by adding n days to the date d. The calculation includes the date d as one of the n days. For example, adding 2 days to 10/31/2003 which is a Friday will give you 11/01/2003 since it counts 10/31/2003 as 1 day and 11/01/2003 (a Saturday) as the second day.
WorkdayAdd([Order Date],7) returns the date seven days after the value in the Order Date field. WorkdayAdd(ToWorkDate(ToDate("10/31/2003")), 1) returns 10/31/2003 while WorkdayAdd(ToWorkDate(ToDate("10/31/2003")), 2) returns 11/01/2003