Hi Sara,
Write the below code on DO_HANDLE_DATA method only. The below code will set the value in 'abc' field when you select the value in 'uname' field. abc is the field in context node.
DATA: wa_form_fields TYPE ihttpnvp,
lt_form_fields TYPE tihttpnvp.
lt_form_fields = form_fields.
READ TABLE form_fields INTO wa_form_fields WITH KEY name = 'uname'.
IF sy-subrc = 0.
me->gv_htm_value = wa_form_fields-value.
wa_form_fields-name = 'dummy_abc'. ""dummy is context node name, abc is fieldname
wa_form_fields-value = 'info'.
INSERT wa_form_fields INTO TABLE lt_form_fields.
ENDIF.
CALL METHOD super->do_handle_data
EXPORTING
form_fields = lt_form_fields
global_messages = global_messages.
Now the setter method of 'abc' field will be triggered and the value will be set.
If you want to set the value in the field which is made from htm page then you just need to set the attibute of impl class as you did for uname,
Let me know in case of any queries.
Thanks,
Ritu