field not found  & exists() function

hello,

I have a script where I want to load a field (field 1) from different CSV files.

The field exists in some of the files, but not all of them.

For the fields where [* Income Treatment]  does not exist, I want the script to create a new [Income Treatment]

For the fields where  [* Income Treatment] does exist, I want the script to load it as [Income Treatment]

this in order to have at the end 1 field "field 2" with the concatenated fields.

I tried to use error_mode = 0; & error_mode = 1; but it doesn't work.

Then I tried to use the function exists() but still it doesn't work.

Can you help to order my script to make it work? Thanks a lot!

FYI below original part of script

[Investment Universe]:

        LOAD

            Num(PurgeChar([Year Month], '-')) as [%YearMonthID],

            [ISIN]        as [%IsinID],

            Null()        as [Internal Fund Type],

            1          as [IsInUniverse_],

            'External'       as [Fund Type],

            'In'        as [Investment Universe],

        FROM

            [$(vL.ExternalFundFile)]

            (txt, codepage is 1252, embedded labels, delimiter is ';', msq)

        Where

            Len(Trim([ISIN])) > 0

            and

            Num(PurgeChar([Year Month], '-')) >= $(vL.FirstDateToLoad_Metrix)

             ;