Sure thing..
This is built with five assumptions:
1) you want to do this across multiple groups
2) you may not know the number of values that you have to multiply
3) there may be negative values in the multiplied values
4) none of the rows have missing values
5) there may be fractional values less than one in the records.
The tile tool is creating two sets of record IDs. One for each group, and then a record ID within each group. This will be important later.
The multi-row formula tool is where we're actually doing the multiplication with
IF ISNULL([Row-1:Field]) THEN 1*[Field] ELSE [Field]*[Row-1:MULT] ENDIF
We have the group by set on the grouping fields, and set values for rows that don't exist to null.
So, the first row in every group checks for "Row-1", which doesn't exist, and so the above setting says that value is null. Our formula checks and says then multiply 1 against the field value to keep it the same. this only really applies for the first row in our dataset. For every other row, look at the multiplication total in the row above and multiply it by the value in the current row.
At this point we sort the records by the tiled field we created earlier ([tile_num]) and then by the sub-record ID ([tile_sequencenum]). We're sorting the records by the sub-record ID descending to ensure that the last value is the first record we see. We're doing it this way because the sample tool used next doesn't have a "Last N records" option. Also we're doing this (instead of taking the maximum value in the grouping set) because it's possible that your records have negative values in it, or maybe fractional values less than one.
The sample tool used last then takes the first record per group so we have our summary of each multiplied value.
let me know if there's any questions.
