Power Query: Custom column to sum revenues for remaining months based on selected month number

Hello Abourard, 

Try this M code in Power Query. It filters months greater than your selected month and sums their revenues. You can either use a parameter for one forecast point or calculate it row‑by‑row:

1. Using a parameter (single forecast point)

let
    Source = YourTable,
    SelectedMonth = 5,   // or create a parameter
    RemainingMonths = Table.SelectRows(Source, each [MonthNumber] > SelectedMonth),
    SumRemainingRevenue = List.Sum(RemainingMonths[Revenue]),
    Result = Table.AddColumn(Source, "RemainingRevenue", each SumRemainingRevenue)
in
    Result

2. Row‑level calculation (each month forecasts the rest of the year)

Result = Table.AddColumn(Source, "RemainingRevenue", 
    each List.Sum(
        Table.SelectRows(Source, (r) => r[MonthNumber] > [MonthNumber])[Revenue]
    )
)

Use the parameter approach if you want one forecast based on a chosen month, or the row‑level approach if you want every month to show its own “remaining months” total.