Since changing records does not change data nor your found set, I don't see why that would change a total, so you need to explain that in more detail.
There is a script trigger that you an select inside Layout Setup, OnRecordLoad that will be tripped each time you change records by any means. This might do what you need.
Here's what I am doing:
I made a checkbook app. Each entry in the month has a category. I want to see how was spent for each category for each month as I cycle through the months. However, when I switch months (each month is a record) the totals don't change because I don't know what trips when you change a record.
I will definitely check out OnRecordLoad- I think that was what I am looking for. Thanks!!!
If you have things set up correctly, I don't think that you'll need any script. A relationship from a "month" record to a record of check book transactions should make it possible to see a subtotal from just the records for that month update automatically when you change records.
You may find this thread on a "Bookkeeping Ledger" of interest: https://dl.dropboxusercontent.com/u/78737945/AccountingLedger.fmp12