you already had the solution written here, by some reason it is hidden now.
DO.
ASSIGN COMPONENT sy-index of strcutre wa_1 to <lv_field1>
if ( sy-subrc <> 0 ).
exit
endif.
ASSIGN COMPONENT sy-index of strcutre wa_2 to <lv_field2>
if ( sy-subrc <> 0 ).
exit
endif.
if <lv_field1> <> <lv_field2>.
* this field is different between the structures - do your own logic (e.g. find sy-index's position of the field in fieldcatalog, if it was not changed and highlight the field, or whatever you would like to do). If you need to find the real name of the fieldname in structrue, use e.g. FM DDIF_FIELDINFO_GET, where you can find sy-index's position and the name of the column.
endif.
ENDDO.