Populating fields based on field name in a file

I have a "rules" file whichcontains the following fields:
 
MFD - master field name (a field name in file MMST)
MFV - value for field name above 
EFL - environment file name (could be 1 of 7 for example INVMST)
EFD - environment field name (field name from file named above i.e. DEPT)
EFV - environment field value (value for field name above)
 
the user selects a record in the MMST file (ie. SKU: 12345) and it shoudl then 
populate based on the rules each fo the fields/values in the appropriate 
environment file:
 
Example:
 
Rules file:
 
MFD=CORG
MFV=US
EFL=INVMST
EFD=BUYR
EFV=123
 So if the CORG field='US' in the SKU record selected from the MMST file I want 
the BUYR field in INVMST to be set to 123
 
What I have "tentatively" done (and I don't like it) is shown as a "small 
snippet" below, FYI In the MMST file I have 20+ fields and I have (as of right 
now) 7 environment files which have multiple (5-50 approx. fields)
 
IF MFD='CORG' and CORG (a fld in MMST) = MFV and EFD='BUYR'
eval BUYR=EFV
endif
 
My "befuddled" mind right now sees that I would ahve to this the above for 
EVERY field in in every file??
 
Gotta be an easier way???????????//
 

                
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