I need to find my way to some reference that will explain how to get Filemaker 6 to sum the numbers in a number field, both the total and subgroups as defined by changes in the entries in a sorted text field (20 group labels). Have been looking for this solution for weeks now.

Have you looked at subsummaries? Can you give us an example?

Here is a website that explains my attempt to follow your suggestion:

http://www.siue.edu/~jandris/jimpers/fmprob1.html

Subsummary parts do not appear at all in Browse mode. They appear when you Preview or Print. And -- this is important -- they only appear when you have sorted by the field that you selected when you defined the subsummary part.