I have a calendar with all dates in the year. In the calendar there is a flag field (1 or 0) to indicate if the day was an Invoice day. I am trying to create a field with the count of invoice date in the month. example Feb 2016 has no public holidays so 21 possible invoice day (Mon - Fri). I want Monday the 1st to be 1, Tuesday the 2nd to be 2 and so on. I think I need to combine the rangesum and peek functions to accumulate the flag and create my InvoiceDayOfMonthNumber but I cant figure out how I get it to start at 1 again on the change of a month.