Use a table calc to filter out stuff, and all the rows will still remain in the underlying table so that the total will still be $200.
Post a workbook and I'll show you how to do that if you don't know.
Yup. that article directs you to use a table calc as a filter.
So depending on how Jerry has his sheet working, he would use a table calc to display 30-day or 60-day (or whatever he wants) and only the pertinent marks would get displayed.