To accommodate a "business day" schedule, you must create a process/program that identifies and counts business-day of the month. One method is to determine what days-of-the-week you consider to be business days (not presuming a Monday through Friday schedule), then also define a SAS format that lists the holidays of the year, then also define/test for fixed-dates of every year that are also considered holidays.
With this information and using a SAS program, you can count from the start-date of any month (using the INTNX function) and determine what date is considered the relative third business date of the month.
Scott Barry
SBBWorks, Inc.