Prototypes and parameters

This is a multi-part message in MIME format.
--
[ Picked text/plain from multipart/alternative ]
I have a general-purpose pop-up window used to display and select values
from a reference file.

Parameter 1 is the reference name and it's passed in as a literal ('TERMS',
'STATE').
Parameter 2 is the field I want the value selected by the user returned into
(back to the caller).

Both parameters are 10A.

Currently, the program is called with a prototype using EXTPGM(‘LOOKUP’).  A
typical implementation looks like this:

     C                   callp     lookup('TERMS':q_alpha_10)
     C                   eval      terms_code =
%subst(q_alpha_10:1:%size(terms_code))
     C                   callp     lookup('STATE':q_alpha_10)
     C                   eval      sh_state =
%subst(q_alpha_10:1:%size(sh_state))

Now, the complication: the size of the second parameter varies (based on
what I’m looking up): "terms_code" is 3A, but "sh_state" is 2A.  Improper
management of the parameters (size) has caused problems (decimal data errors
because the improperly-sized parameter 2 overflows into adjacent fields in
memory); the second line solved the problem.

Because LOOKUP is called with EXTPGM, OPDESC doesn’t work.  Yes, it should
be in a service program but circumstances of time and customer politics
don't allow it.

I’ve done this too:

     C                   callp     lookup('TERMS':q_alpha_10)
     C                   eval      terms_code = q_alpha_10
     C                   callp     lookup('STATE':q_alpha_10)
     C                   eval      sh_state   = q_alpha_10

This is the ideal solution:

     C                   callp     lookup('TERMS':terms_code)
     C                   callp     lookup('STATE':sh_state)


I've tinkered with VARYING, setting the length, etc. but am unable to come
up with a way to
implement the ideal solution.  Perhaps it’s too much Halloween candy, but
I'm sure there's a better way to juggle OPTIONS(*VARSIZE) and VARYING to
make this work...or is there?

Thanks,
rf
--