creating a field in a record with limited summary data
I can't figure this out. I have a database with a series of records, dated daily over the past year containing a lot of fields with numerical data from each day. I would like to include a field in each record that contains summary information from a single field- but only from a limited set of records (not the entire record set). ie the current week, or past week, or past month etc. I do not see how to do this. I can find the day of the week and thus the start and end date that I am interested in, but I can not figure out how to limit the summary field (for example the average of, or total of) to those specific dates.
I would like the data to be updated as I add new daily records. Is there any way to do this? It would seem simple, but I have not been able to figure it out.
Thanks for considering.