Pass Parameter as column name in custom column calculation

u could, peraphs use this sheme:

a function like this:

let
    newTab = (Col1,Col2)=>Table.AddColumn(Table, "newColumnName", each Record.Field(_, Col1)-Record.Field(_, Col2))

in
    newTab

which when invoked using the names of two columns of you table:

gives:

I think i figured it out. I modified your Function to be a simple addcolumn step:

Table.AddColumn(PreviousStep, "Delta", each Record.Field(_, #"Scenario 1")-Record.Field(_, #"Scenario 2"))

Where Scenario 1 and Scenario 2 are the query parameter names. Seems to work!