declare 
 mcount char(8);
 a number;
begin
	if :iss.tray_no  is null then
		g.dummy := g.cent('Tray No. Cannot be Blank',1,1);
		 raise form_trigger_failure;
		 go_item('tray_no');
	end if;
   select count(*) into mcount from iss
		where rtrim(lower(tray_no)) = lower(rtrim(':iss.tray_no')) and
		  sl_no <> :iss.sl_no;
      if mcount > 0 then
  		g.dummy := g.cent('Tray No. already exists',1,1);
		raise form_trigger_failure;
	end if;	

a :=	length(':iss.tray_no');
if a != 8 then
	raise form_trigger_failure;
end if;
go_item(':iss.qty');
end;