commitment control scope

Having the following problem and need some suggestions to get around it:
 
**Back Ground info
There is a pgm, I'll call it PGMA, in our system that do a lot of calculation, 
update some files and write records to our AR/AP file.  All update and write to 
files in this program are under commitment control.  However, this program does 
not do commit or rolbk.  Instead, the caller uses the return error code field 
to determine if commit or rolbk is needed.
 
I've a project that required me to get the AR/AP amount that generated by this 
program and display it on the screen without committing any record.  I created 
a service program that basically call PGMA.  After it return back to this 
service program, it read the AR/AP file to get the total then do a ROLBK.
 
**Everything is working fine, except, this service program has a side effect 
the I don't really like:
In our system, the driver program, that takes user to the main menu, starts the 
commitment control with CMTSCOPE(*JOB).  That means, if a program update some 
files with commitment control and call the above service program.  The files 
that it updated will also be rolbk by the service program.
 
My plan was to create this service program in a different actgrp and strcmtctl 
within the service program with the scope of actgrp.  However, I get a error 
saying that the commitment control already started (started by the driver 
program using *job scope).
 
any suggestion on how to get rid of this side effect for this service program?
 
thanks