Determining future date using only workdays
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Feel free to provide a more detailed version of your question.
By "work days" do you mean week days or must you also allow for holidays and other possible nonwork days that happen to fall on a week day? If so, you'll need a list of at least the holidays in a table so that you can allow for them.
I set up a table of working days in a calendar format on one of my solutions such that the users can either enter a date or click a button in the calendar "square" to mark the date as a date that they will be closed.
We can then use a relationship that matches to this record by date, but only for dates where the business is open and GetNthRecord gets us a date N days in the future.
The relationship looks like this:
Invoice::Date < Calendar::Date AND
Invoice::constOpen = Calendar::ClosedOrOpen
The second pair of match fields filters out the dates where the business is closed.
GetNthRecord ( Calendar::Date ; 3 )
Returns a date 3 business days in the future.
Using a modern date API, typically this means using a micro-service, you can easily get future dates given only parts of date info. I've posted many times (Please Search) how you can compute "work days" in multiple ways -- using any day or days of the week, custom holidays, etc.. Combining that with a simple lookup for the date for one of the work days would be trivial.
As philmodjunk suggested, however, for maximum help here you should post a problem statement, desired outcome examples, and maybe a design screenshot or two.
Retrieving data ...