If you use this piece of code then you doesn't need the interval match anymore. While 'Startdate + ITERNO() - 1 <= Enddate' is TRUE a new row is generated and ITERNO() is the row counter. So first iteration ITERNO() is 1. Therefore -1 after ITERNO() to correct this offset. First iteration is Startdate + 1 - 1 equals Startdate, second iteration is Startdate + 2 - 1, equals Startdate + 1. Etc.