PL/SQL :: Aggregated Functions Moving Value One Row Down

this query

SELECT
      shrtgpa_pidm,
    shrtgpa_term_code,
    sum(shrtgpa_hours_earned) over (
   partition by shrtgpa_pidm
   order by shrtgpa_term_code

[Code]....

retrurns this rsult

82724     201010     4.5     201010
82724     201020     9     201020
82724     201110     13.5     201110
82724     201120     17.5     201120
82724     201310     20.5     201310

I need to be able to displayu the 4.5 in 201020 9 in 201110 in another words I need to move the results one term down

how I can do this?

I am thinking in a sequence? so 201010 will be seq 1

201020 will be seq 2
201110 will be seq 3
etc..etc..the I can do an update

Can this be done with aggr sql func? If not how I can add a sequence in the query It needs to break by shrtgpa_pidm

I need to end with these results
201020    4.50
201110    9.0
201120   13.50
201210    17.50
201220    21.50       

here is the code to withe a table with data

create table testgpa
(
  testgpa_pidm                 NUMBER(8)            NOT NULL,
  testgpa_term_code        VARCHAR2(6 CHAR)     NOT NULL,
  testgpa_hours_earned    NUMBER(9,3)          NOT NULL
  )
 
[Code]....