how to populate the field when the field name is stored as variable?

Hi
I have to populate a file, but the field names of that file are stored as 
variables in another file. How can I populate the first file? Please help. 

Here is the example:

File1:
Fields are:     ITMNUM   (Item Number)
                CATCOD  (Category code)
                DISCDT   (Discontinue Date)


File2:
BEGTAG          ENDTAG       FIELD              FILE
(Beginning Tag)              (End Tag)               (Field To Populate)     
(File to Populate)
----------------------  -----------------            -------------------------  
  -----------------------
<prod-number>           </prod-number>     ITMNUM                      FILE1
<category-code>            </category-code>   CATCOD                    FILE1
<disc-date>             </disc-date>            DISCDT           FILE1


Now, according to file and fields names in File2, I have to write records in 
file1. How can I use the file and field names that are stored as variables in 
file2 using RPGLE? 
I was thinking may be I need to use pointer. But I never worked with pointers 
in RPGLE before.

Please help.

Thanks in anticipation,
Amitava