I'm not sure to understand your problem... can you describe it in more details?
The format is basically like that:
CODEPAGE:XXX
GROUP_FIELD_NAME:name_field1
GROUP_FIELD_VALUE:my_value_1
...
GROUP_OFFSET:0
GROUP_LENGTH:0
GROUP_FILENAME:my_filename.out
And the order for the pairs GROUP_FIELD_NAME/VALUE are not important, except that first you must have GROUP_FIELD_NAME followed by GROUP_FIELD_VALUE.
Then you had the very old format of the .ind, which is not anymore valid (ended with CMOD V9.x, and maybe also removed with CMOD 8.5.0.6+, but not 100% sure) where you needed to put all the index field name at the beginning of the file, and then following this "header", you put the values of each documents sequentially.