Getting a Pointer to a Job

To All,
 
I thought that there was a (short) discussion about how to get a pointer
to any job on the system, that can be used as input to the second parm
of the MATINVS command to get the Invocation Stack for the job; but now
I can't [ f i n d ] that thread.  At any rate, I just browsed through
Chapter Nine of Leif's book ("The Work Control Block Table") about how
to find a job on the system.   Using the Machine Index QWCBT_JOB_INDEX
seems to me to be a neat way to find the WCB enty for an arbitrary job.
 
Once the WCB entry is located, where can we get the system pointer to
the job [ i t s e l f ]?  Chapter Nine shows part of the WCB entry as
follows:
 
 
DCL DD WCB-ENTRY CHAR(1024) BAS(.WCB-ENTRY);
    DCL DD WCB-DEVICE    CHAR(10) DEF(WCB-ENTRY) POS(  1);
    DCL DD WCB-USER      CHAR(10) DEF(WCB-ENTRY) POS( 11);
    DCL DD WCB-NUMBER    CHAR( 6) DEF(WCB-ENTRY) POS( 21);
    DCL SYSPTR .WCB-PCS           DEF(WCB-ENTRY) POS( 33);
    DCL DD WCB-TYPE      CHAR( 1) DEF(WCB-ENTRY) POS( 97);
    DCL DD WCB-STATUS    CHAR( 2) DEF(WCB-ENTRY) POS( 98);
    DCL DD WCB-GROUP     CHAR( 1) DEF(WCB-ENTRY) POS(100);
 
So, is the .WCB-PCS pointer the magic-bullet that will locate the job?
Forgive if this seems like a dumb question.  I looked at all the Apis
that I could find that retrieve job information; there doesn't seem to
be any that will return a pointer that will work with MATINVS.  Not
surprising!  So I guess that MI is the only way to do it.
 
Thanks,
 
Rich Hart