also found this thread that refers to calling the workday function (or any function) from excel to be used in access
https://msdn.microsoft.com/en-us/lib...ffice.12).aspx
it covers how to get your data into a form suitable to be used by the function. in essence
Code:
Function UseExcelWorkdayFunction() as long
'install excel xx.x object library in references
Dim xl As Excel.Application
...
...
get your data into form required
...
...
Set xl = New Excel.Application
UseExcelWorkdayFunction = xl.WorkDay(start date, days, [Holidays])
set xl=nothing
End Function