one way is to save the target date in a variable, assuming you have a field DATE that user selects: vPrior2Days = date(bus_dt.autoCalendar.date -2) thinking second to last date is 2 days prior to the selected date.
then in your set analysis you can use the modifer: {<bus_dt.autoCalendar.date ={'$(vPrior2Days )'}>}