How to use expression (x,y,z)

My target is to have multiple steps, as written here:

(
Input_Table as table,
InputColumnToChange1 as text,
InputColumnToChange2 as text
) =>

let
List1 = Input_Table[InputColumnToChange1],
List2 = Input_Table[InputColumnToChange2],

NewTable1 = Table.ReplaceValue (
Input_Table,
each [List1],
each if [List1] = "Bronze"
then "StSt 316L"
else [List1],
Replacer.ReplaceText,
{List1}
),

NewTable2 = Table.ReplaceValue (
NewTable1,
each [List2],
each if [List2] = "Bronze"
then "StSt 316L"
else [List2],
Replacer.ReplaceText,
{List2}
)in NewTable2

I want to invoke them in this way:

let
Source = #"Query1 (2)"(Summary_Volumes, "Body_Material", "Stuffing_Box_Material")
in
Source

but I don't understand why I have the error message:

Could you support me on the error?

Thanks.