declare 
 i   DATE;
begin
   i:=:p50_X; 
 while (i <= :p50_Y ) loop
 update invent 
          set DATESPIS=:p50_DATESPIS   
 where DATEPOST = i; i := i +  1 ; DATESPIS is null; 
 --where DATEPOST = i; i := i + 1;

  end loop;
end;