I have this form with multiple components in it

first part is an simple form. I have a custom plsql page process to insert the form data.
I'm using
RETURNING REQUEST_ID into :P11_REQUEST_ID;
to get back the PK regenerated, request_id is my FK to be used in master-detail IG.
I know for single IG we can use
begin
case :APEX$ROW_STATUS
when 'C' then
//insert
when 'U' then
//update
when 'D' then
//delete
end case;
end;
But how to write plsql code for master-detail IG.
Any Help is really appreciated
Thank you