I think what @Tim is asking is on which day during any week do you start being concerned about looking at "next week's" schedule? Is that a clearly defined rule? (ie. up until Thursday you're always concerned with looking at this week's workbook, then Friday onwards you're looking at next week's schedule?). Obviously, if you say that the workbooks are sometimes created on Monday, but sometimes not until Tuesday, that's not necessarily ideal in terms of coding set logic. Otherwise, if your code is being triggered in a "master" spreadsheet, then just have a cell where you set the "this week" / "next week" parameter, and use the value of that cell to determine your "8 / 15" switch