I have a stock table that contains week number, in this case the weeks run from week 18 to week 41. I am trying to write a query that will combine week into months. A complication, is that the starting week numbers increment every week so that next week, the week number swill be week 19 to week 42. Basically Week 18 will drop off and week 42 will be added to the table. I want to be able to aggregate the weekly values into monthly values in a environment where starting and ending weeks increment from week to week. I've exported the table to an excel sheet and have attached the sheet.