Packola has a mechanism for the carbuncle figure. That number which represents a one-off situation and which doesn't fit into the regular calculation. Perhaps its an exchange rate adjustment to cover the recent huge shift in rates. Perhaps its a reserving position which you may or may not want to include in the return.
We call these Special Cases. You can define as many as you want, and then replace different cells with that value. If you change the Special Case, all the related cells are changed. You can put it in an adjustment or a formula by referring to the case's name, not its value.
