Power Query Sum within grouped data

Hello,
Work book attached with examples.

I'm trying to sum figures in grouped data for each group, so I have the groped data ;

Table.Group( #"Integer-Divided Column",{"Index"}, {{"ALL", each _ }} )

and I wan to sum a 'sales' column within the group, so if I were adding an index to to each grouping i'd put this after each ;

 Table.Group(#"Integer-Divided Column", {"Index"}, {{"Count", each Table.AddIndexColumn(_ , "IndexG", 1, 1, Int64.Type ) }} )

So I'd like to use list.sum in a similar way, but can't get it to work,

each _ List.Sum( [Sales] ) }} ) , List.Sum( _ [Sales] ) etc. don't seem to work.


i've exapneded one group and done the calculation on that group as I thought I might be able to make it a function, but couldn't get it right;

 Table.AddColumn(#"1", "Custom", each
                                                  [Sales] /  List.Sum( Custom1{[Index=1]}[ALL] [Sales]), Percentage.Type)

So I've like to get what i have for a single group, above, for each of the All Rows grouping,

Richard.