Here is a solution we use for getting dynamic info into a job stream file.
It does not require MPEX, it uses QEDIT, but could used EDITOR instead

    1     cls
    2     COMMENT ******************************************************
    3     COMMENT * NOTE:  DO NOT MODIFY THIS FILE !!!!!!!!!!!!!       *
    4     COMMENT * This job is setup to prompt for:                   *
    5     COMMENT *  - period of the claim purge (1 quarter)            *
    6     COMMENT * Job CLMPURGE will be streamed by this command file *
    7     COMMENT ******************************************************
    8     echo command file: CLMPURGE.SMARTJOB.MSL3000
    9     echo
   10     input qtrdate, "Beginning/Ending period, (ex. Oct-Dec 2000):"
   11     echo
   12     echo The parameter entered is:
   13     echo   Beginning/Ending period of Claim Purge - !qtrdate
   14     echo
   15     input promptyn, "Is this correct (Y/N):"
   16     setvar promptyn ups("!promptyn")
   17     if promptyn = "Y"
   18       echo
   19     else
   20       echo Run Terminated by request
   21       return
   22     endif
   23     purge printo,temp >$null
   24     purge tmpjob,temp >$null
   25     build printo;temp;rec=-80,,f,ascii;disc=1000
   26     file printo,oldtemp
   27     file tmpjob;temp;rec=-80,,f,ascii;disc=1000
   28     print clmpurge.smartjob.msl3000;start=35;out=*printo
   29     run qedit.pub.robelle;parm=4;&
   30     info='set interactive off;t *printo;&
   31     cq"{q}"!qtrdate"[/];&
   32     k tmpjob;e' >$null
   33     stream tmpjob
   34     return
   35     !job CLMPURGE,manager.msl3000;outclass=lp,1
   36     !setvar QTRDATE '{q}'
   37     .......
   38     !EOJ


- execute the command file from a session
- line 10 prompts for a parameter value
- lines 11-22 display value and verify that the value entered is OK
- line 28 'prints' the command file starting at line 35 to a temp file
- the qedit execution on 29-32 scans the file looking for {q} and
   replaces it with the parameter value
- line 33 streams the temp file
the variable QTRDATE now has the parameter value enter by the user

there are ways to perform this, but this works for us.

regards,
  Robert