Writing a CL to save changed objects from *ALLUSR libs

Hi all,

I would like to make a SAVCHGOBJ on *ALLUSR libraries to disk, not to tape. 
Goal is to send it to a backup system. To save into files, I have to create a 
file per library because SAVCHGOBJ *ALLUSR doesn't work when saving on file. So 
I wrote a CL that first lists *ALLUSR libraries, then creates a file with the 
name of the library to save and then saves. Here it is :
PGM                                                                   
             DCLF       FILE(SAVES/LSTLIB)                            
                                                                      
             DSPOBJD    OBJ(*ALLUSR) OBJTYPE(*LIB) OUTPUT(*OUTFILE) + 
                          OUTFILE(SAVES/LSTLIB)                       
LECTURE:     RCVF                                                     
             MONMSG     MSGID(CPF0864) EXEC(GOTO CMDLBL(FIN))         
             IF         COND(%SST(&ODOBNM 1 3) *EQ 'SAV') THEN(GOTO + 
                          CMDLBL(LECTURE))                            
             CRTSAVF    FILE(SAVES/&ODOBNM)                           
             MONMSG     MSGID(CPF7302)                                
             SAVCHGOBJ  OBJ(*ALL) LIB(&ODOBNM) DEV(*SAVF) +           
                          SAVF(SAVES/&ODOBNM) CLEAR(*ALL) SAVACT(*LIB)
             MONMSG     MSGID(CPF0001 CPF3702)
             GOTO CMDLBL(LECTURE)             
FIN:                                          
ENDPGM                                        

It works fine, but I would like to know if something has been saved into file 
to delete it if not. I see 2 ways :
- When SAVCHGOBJ saves some objects, completion message CPC3723 is sent, and 
when nothing is saved, message CPC3708 is sent. But basic MONMSG doesn't work.
- DLTF save file before creating it and test if file is empty after SAVCHGOBJ. 
But how ? It must be so simple, but I have no idea.

Some idea ?

Thanks.
Best Regards.