Passing paramater on to List.Range function

Hello everybody,

I am currently trying to feed the List.Range function with parameters via a custom function, which sadly does not seem to be working.

The custom functions extract a value from the following spreadsheet table:

The custom function looks like this:

(ParameterName as text) =>
 let
     ParamSource = Excel.CurrentWorkbook(){[Name="tblParameter"]}[Content],
     ParamRow = Table.SelectRows(ParamSource, each ([Parameter]=ParameterName)),
     Value=
	if Table.IsEmpty(ParamRow)=true
	then null
	else Record.Field(ParamRow{0},"Value")
in
    Value

The custom function returns the correct result:

Yet when I insert the value returned by the custom function into the following formula, things go south:

= Table.SelectColumns(Source,List.Range(Table.ColumnNames(Source),0,14))

= Table.SelectColumns(Source,List.Range(Table.ColumnNames(Source),0,fnGetColumn("Submitted Forms: to Column")))

I am getting this error:

If I were to use a Power Query parameter, though, the List.Range function would accept it. But I need to extract the value from the spreadsheet.

Hope someone can help me out here!

Best regards!