I hope I have the correct forum.
Within Power Query I am trying dynamically add columns based on an input from Excel.
The input would be something like this from a cell within Excel (I point a query to this cell)

The above could be selected as Jan, Feb, Mar etc to Dec.
The data has this structure:
| | Jan | Feb | etc. | Nov | Dec | YTD | |
Sales | 100 | 100 | | 100 | 100 | 200 | |
| Expenses | 50 | 50 | | 50 | 50 | 100 | |
| | | | | | | | |
I would like to sum the columns Jan to Feb (in this example) into the YTD column dynamically based on the earlier input.
Is this possible?
The formula is easy in Excel but I'm struggling within Power Query.
What is the M formula?
Thanks in advance for any help