CL source file searching for a specific library name

I am writing a program that reads through a CL source file searching for a specific library name (PANDPGM or PANDFIL)...

if found the hard coded library will be replaced by a variable (&pgmlib or &FILLIB) and some code will be inserted to retrieve these libraries from a message file. I am using RPGIV and attempting to use %scan %replace but am not having much success. Could you provide an example?

Here you go:

 
C                   EVAL      ScnPos = %SCAN('PANDPGM': SRCDTA)    
C                   If        (ScnPos > 0)                         
C                   EVAL      SRCDTA = %REPLACE('&PGMLIB': SRCDTA: 
C                               ScnPos: 7)                         
C                   End                                            
C                   EVAL      ScnPos = %SCAN('PANDFIL': SRCDTA)    
C                   If        (ScnPos > 0)                         
C                   EVAL      SRCDTA = %REPLACE('&FILLIB': SRCDTA: 
C                               ScnPos: 7)                         
C                   End