I have an Access 2003 database that has weekly dates and weights enter for a weight loss program. Ech program session is 8 weeks and people sign up for anywhere from 1 to many more sessions at a time. I want to find out the average weight lost in the first 8 weeks that a patient belongs, then in 16 weeks and so on. However, not every patient has every week entered and all pateints start on different weeks (but the weigh ins are always Wednesdays. Is there a way to pull the dates and weights from everyones first session, second session, and so on? I have tried doing [initial date] + 56, dateadd [ww, 8, initialdate] and CountofDate but none have pulled more than 25% of the patients.