How to return a value when the fields don't match in SAP Infoset

I have the main table EKPO joined to tables MLGN and MLGT as outer joins.

I have created an extra field BINALOC in the infoset and want it to return a value from table MLGT under certain conditions:

1. If the fields MLGN-LTKZE and MLGT-LGTYP match then return the associated MLGT-LGPLA field.
2. If MLGN-LTKZE = 'R1', then only return relevant MLGT-LGPLA where MLGT-LGTYP = '006'.
3. If MLGN-LTKZE <> MLGT-LGTYP return blank.

Currently I can do the first 2 conditions but unable to fit in the 3rd as it conflicts with the number 2.

I have tried a variety of IF statements and various orders for the IF conditions, and different join types.

This the current code I have in the extra field BINALOC coding section:

IF MLGN-LTKZE = 'R1'.
  select LGPLA as LGPLA
   from *MLGT into BINALOC
   where *MLGT~LGTYP eq '006'.
  ENDSELECT.    
else.
  select LGPLA as LGPLA
    from *MLGT into BINALOC
    where *MLGT~LGTYP eq MLGN-LTKZE.
  endselect.
endif.

I want the field to return blank when the fields I mentioned before do not match.

Currently it returns a copy of the field above it.

this?

IF MLGN-LTKZE = 'R1'.
  select LGPLA as LGPLA
    from *MLGT into BINALOC
    where *MLGT~LGTYP eq '006'.
  ENDSELECT.
else.
  select LGPLA as LGPLA
    from *MLGT into BINALOC
    where *MLGT~LGTYP eq MLGN-LTKZE.
  endselect.
  if sy-subrc ne 0.
    select LGPLA as LGPLA
      from *MLGT into BINALOC
      where *MLGT~LGTYP ne MLGN-LTKZE.
    endselect.
  endif.
endif.