another excellent reason not to use repeating fields...
set up related tables instead, then sub-summaries are easily achieved
Note that FileMaker actually has a fairly simple process you can use to create a new related table and import the data from the repetitions of your repeating field(s) into individual records.
The import as individual records worked like a charm Phil!!!
I understand there are a lot of ppl that HATE repeating fields, but there are many advantages to using them for some users. I believe I've been using them since FileMaker 4 or 5 (1994).
It's only every so often I may need to change my perspective on how to utilize them for an alternate purpose in a different solution.
I don't hate them myself. I find them useful. But only very, very rarely are they a better option than using a related table of records.