Table.Group sum up dynamic columns

[borlip]

I have a pivoted table where each column represents revenue data by week starts. Week starts are column headers. There could be various number of columns.

I need to sum up each column (total revenue by week). I was thinking to use Table.Group

(table as table, key as any, aggregatedColumns as list, optional groupKind as nullable number, optional comparer as nullable function) as table

aggregatedColumns should be something like this: {{"1/7/2015", each List.Sum([1/7/2015]), type number}....

But how can I generate it on fly for a dynamic list of columns, as I don't know how many columns do I have?

[borlip]

Got away without using Table.Group()... Unpivoted the table and grouped by dates to calculate sum of revenues per each date. Then pivoted the table by dates again...