Problem with convertToString service and outbound flat file

Hello,
i’m a beginner on WebMethods 6.01 and french too. Good luck to understand. My flat file schema is following:

|header (record reference; 1 occur)
*field def1 (position 0)
*field def2 ( 1)
|mesure (record reference; unlimited)
*field def3 (position 0)
*field def4 ( 1)

RecordParser: delimiter
Record Character: \n
field: ;

I want to transform this in a cvs file with the service pub:flatfile:convertToString. The problem is the result in the string output with this service. In fact, the record reference (header and mesure) overwrite the first values of fields. Like this:
headerfield2
energyfield4
energyfield4

If i set the position field to the number of character of header (it is 6 char here) + 1 and the number of character of energy +1, so the values are extract after the name of the two fields. Like this:
header;field1;field2
energy;field3;field4
energy;field3;field4

And it’s good but the schema is so static. An idea to resolv this problem. Thx. See you
Roum

Can you elaborate more on the above positive result part?

And before mapping convertToString are you seeing the header and mesure(list) fields correctly as expected in the pipeline.
what parameters are you setting in the convertToString service?

Thanks,