Have this Formular and work fine. Output is a date:
FirstWorkDate(Max(DBDate), 3, $(Holidays))
When I use this in a filterbox to filter Data from Datedimension "DBDate" got an invalid dimension. I guess the problem is this: Subtracting 3 days from the common calendar and not from the DBDate-Datedimension. So in the end the filterbox has a unassociated date which is not part of the DBDate-Datedimension. Could that be? If yes, have anybody a workaround?