Automate additional Columns in Power Query

[ecrodrig]

I have a data source with months of the year. Each month I add a new column for the current month. An example I currently have Jan - July and then a Totals Column. Everything shows up fine in Power Query but when I add August the August column is showing up after the Totals Column rather than the July Column. I see where the issue is. The Column headers are hard coded. I needed to duplicate a column and once I reordered that column it hardcoded the headers. How can I automate it so that the headers are not hard coded? I was able to fix a previous issue where it wasn't detecting any new columns now I just need to figure out how to automate the hardcoded headers.

Any help is appreciated. Thanks

 

[JGordon11]

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    Months = List.Accumulate({1..12}, {}, (s,c)=> s & {Text.Start(Date.MonthName(#date(1,c,1)),3)}),
    tcn = Table.ColumnNames(Source),
    typelist = List.Accumulate(tcn, {}, (s,c)=> if List.Contains(Months,c) then s & {{c, type number}} else s),
    tbl = Table.TransformColumnTypes(Source, typelist),
    MonthColumns = List.Zip(typelist){0},
    tbl1 = Table.AddColumn(tbl, "Total", each List.Sum(Record.ToList(Record.SelectFields(_, MonthColumns))))
in
    tbl1

Book2
	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S
1	Product	Misc.	Jan	Feb	Mar	Apr	May	Jun		Product	Misc.	Jan	Feb	Mar	Apr	May	Jun	Total
2	A	100000	4655	6119	8372	9836	1234	1000		A	100000	4655	6119	8372	9836	1234	1000	31216
3	B	100000	1572	6524	9580	11967	2345	1000		B	100000	1572	6524	9580	11967	2345	1000	32988
4	C	100000	4318	9295	3566	5078	3456	1000		C	100000	4318	9295	3566	5078	3456	1000	26713
5
Sheet1