Doing a SET with variables

Continuing education:

I am attempting to update a file (table) in embedded SQL in RPG, with
built-up variables:

     D UpdateOne       S            500A   INZ('Update -
     D                                     $AUDITSTG/SAVHISTORY ') 

          // Define SET statement                                       
          if JRFNAM <> #S3FNAM;                                         
             Set = Set + ' JRFNAM = ''' + #S3FNAM + ''' ';              
          endif;                                                        
                                                                        
          if JRVOL <> #S3VOL;                                           
             Set = Set + ' JRVOL = ''' + #S3VOL + ''' ';                
          endif;                                                        
                                                                        
          if JRSEQ <> #S3SEQ;                                           
             Set = Set + 'JRSEQ = ' + #S3SEQ + ' ';                     
          endif;                                                        
                                                                        
          if JRSSIZ <> #S3SSIZ;                                         
             Set = Set + 'JRSSIZ = ' + #S3SSIZ + ' ';                   
          endif;                                                        
                                                                        
          if JRNOTE <> #S3NOTE;                                         
             Set = Set + ' JRNOTE = ''' + #S3NOTE + ''' ';              
          endif;                                                        
                                                                        
          // update record...                                           
          SelectTwo = Update + Set                                

 
//********************************************************************
       // $UPDATE - Update Current Record
*
 
//********************************************************************
       begsr $UPDATE;
      /END-FREE
     C/EXEC SQL
     C+  <------------ (What is the proper way to build this statement?)
     C/END-EXEC
      /FREE
       endsr;                                     

I'm attempting to update only the fields that change. When I attempt to
use a variable, it says that the "Token" was not valid.

TIA

Dave