Capturing jobs from the individual job logs is NOT the way to go.
When a job starts, and when a job ends, you will see messages like
CPF1124 - Job 170987/QPM400/Q1PPMCHK started on 10/30/07 at 10:00:12...
CPF1164 - Job 170987/QPM400/Q1PPMCHK ended on 10/30/07 at 10:00:13; ...
Now that you know these two message id's you can do a
DSPLOG PERIOD((...specify date and time for "from" and "to"...))
OUTPUT(*PRINT) MSGID(CPF1124 CPF1164)
Alas, there is no *OUTFILE option on this. Only screen or print.
So, you can use iNav to copy that spool file to a .txt file on your PC and
analyze that to your hearts content.
Not really finding an API that would fit the bill here at