Ok...after several weeks (can only work on it in free time) of struggling with extracting the summary data into an indexed field I can use for other calculations, I tried an auto-enter Calculation (rather than a Lookup or GetSummary or Calculation) field in the Invoices table of the Summary field in the Appointments table. It seems to work.
However, I am still stumped as to how to get and preserve the past and current quarter totals so I can forward them. Perhaps I must use a Payments table?
You may want to look into the getsummary calculation. This will get the summary value based upon the value of a break field. You can filter values through a relationship; the calculation does not necessarily have to be in the same table unlike the summary field.
I hope that helps.
Thanks for your response. I did try getsummary in a Calculation field, but was unable to index it. I think the solution I found yesterday (a Number field using auto-enter Calculation [=Appointments::Summary]) is working surprisingly well. However, I still don't know how to save a balance from one quarter to be added into the total of the next quarter. Do I need a recursive relationship? If so, what is this?
Thanks again and in advance!