Problem with customizing a DFF in custom.pll

Hi all !

I have a DFF with 10 fields, some are required and some are not. In certain cases, they should

all be non-required. I tried the following in custom.pll :

     IF (event_name = 'WHEN-NEW-RECORD-INSTANCE' AND form_name = 'ARXTWMAI') THEN

      app_item_property2.set_property( 'TGW_HEADER.DESC_FLEX_MIR' , REQUIRED, PROPERTY_OFF);

     END IF;

compiled, logged in to OA again, but it had no effect. I think it's the part "TGW_HEADER.DESC_FLEX_MIR" that might be wrong.

Do I have to reference every field I want to make non-required ?

And what I'm I supposed to put in ? In Forms Builder, the block is called "TGW_HEADER" and the dff-item is "DESC_FLEX_MIR".