Mapping multiple OBX segments to multiple FRL fields in ADTs

I need someone’s guidance on how to map numerous (different) user defined fields coming in OBX 3.1 from HL7 2.3 ADTs to go to different FRL fields outbound. There is no consistency as to what segment it will come in (like SET ID), if at all for that field.  

Example:

OBX3.1 can equal any one of the 50+ different FRL fields depending on what is sent and I need to equate what is sent to a corresponding FRL field.

I’m used to using iterates for OBXs going to same outbound field, this is new for me and any suggestions are appreciated.

Thanks in advance,

Jim