Sorting records and performing a find are two different operations.
Portals do not have found sets, that's a function of a layout, not a portal.
To show different sets of records in a portal, you either manipulate the values in match fields to match to different sets of records or you manipulate a value used in a portal filter.
Thanks -- changed so I was using a layout instead. Any idea how to create a formula in which I can get the decay rate on a summary? i.e. the summary of revenue from month 1 --> the revenue of month 2? I want to see what the drop in revenue was.
Much will depend on how the data is set up in your table, presumably you have multiple records for each month. But a self join relationship can be set up to match to the previous month's set of records in order to subtract the tsubtotals.
Say each record has a date field named TransactionDate.
cMonth could be a calculation field with date as its result type defined as:
TransactionDate - day (TransactionDate ) + 1
cMonthPrev could be defined as:
Date ( Month ( TransactionDate ) - 1 ; 1 ; year ( TransactionDate ) )
Then this self join relationship:
YourTable::cMonthPrev = YourTable 2::cMonth
will matc a record in YourTable to all records dated from the previous month in YourTable 2.
YourTable::cMonth = YourTable 3::cMonth
would match to all records of the same month.
Sum ( YourTable 3::amtField ) - Sum ( YourTable 2::amtField )
would then compute the difference you described.
YourTable, YourTable 2, and YourTable 3 would all be different Tutorial: What are Table Occurrences?.
PS. by adding an additional pair of match fields to both of these relationships, you can refine the matching to a subset of the records for a given month such as all records with the same accountID or ProductID from the previous or same month.
ExecuteSQL in FileMaker 12 or newer could also compute these totals without the need to add more relationships and table occurrences to your relationship graph in Manage | Database.