Allow order of CUMULATE function to be defined by the user

The CUMULATE function when used against a list, currently accumulates in the original list order even when the list has been reordered. Anapedia states this is how the function is meant to work, but I would like it to take into account if the list has been reordered, and cumulate in the new order.

Description of the enhancement required:
The addition of a new optional parameter to the CUMULATE function which will enable the order of accumulation to be changed when used against custom lists. By default the order of accumulation is based on the initial order of the custom list when the list was created, however it would be useful to have control of whether to cumulate over the order of the original list or the reordered list.

An example of the enhancement:
CUMULATE(Line Item, TRUE/FALSE, List, Original order/New order)

Use case/how this would help business process:

Within our models we use custom lists which is a time dimension expressed in the number of weeks before a given event. When we tried to accumulate revenue along the life of the event, the CUMULATE function was doing this in the wrong order (building from the week of the event instead of the week furthest from the event). It was quite a challenge to correct this and we needed to delete and re-upload this list in the reverse order. If the cumulate function was more flexible this would not have been required.