Depends on the version of excel If you are using the 2007 version, you can simply use the SUMIFS, AVERAGEIFS, COUNTIFS, etc. functions. Link to MS Explanation If you are using the 2003 version, you will probably want to use the DSUM, DAVERAGE, DCOUNT, etc functions. Link to MS Explanation If you’re wanting to do pivot tables and/or graphs you might need to make each week’s data fall into an exact date. Ex. Have an equation that makes 10/25/09, 10/24/09, etc into 10/19/09. This could be done by the DATE function and the WEEKDAY function.