Mozart/Oz : convert string to feature

I need to generate features names that I don't know in advance, in order to make a record.
The record should look like:
record(day1:[...] day2:[...] day3:[...] ...).
As I don't know how many days the record will contain, I cannot write features names by myself! I tried several things:

{For 1 N 1
proc {$ I}
  local 
    Label 
    Day="day"
  in
    ...
    % Label=Day+I 
    % cannot add a list and a number

    % Label={List.append Day {Int.toString I}} 
    % creates the right string, but when trying to make the record: type error

    % Label=dayI 
    % works but produces only "dayI" features, all the same

    % Label=day + I
    % cannot add a feature and a number
    ...
  end
end
}

All Labels are then processed in a list, in order to use Record.makeTuple.

Is there any way to create dynamic features, or manipulate them?
For now, the only alternative I found is to use the string, not as a feature but with a pair : record("day1"#[..] "day2"#[..] ...) but this is not what I want.

Thanks for any answer or help.

The features of records are atoms. To convert a string to an atom, use String.toAtom. For example:

declare
L = {String.toAtom "dynamic string"}
R = {MakeRecord record [L]}
{Show R}

However, if I remember correctly, there is a caveat: atoms are not garbage-collected. If you create very many different atoms, you might run into memory problems.