How to build a flow field from another flow field without any hardcode

I am expecting to build a lookup flow field that comes from another lookup flow field from another table. what i am doing was only to add on table level. how can i add that without any hard coding?

take this for example.

Table A,
Field Name ( normal )
Field PostCode ( normal )

Table B
Field No
Field PostCode ( Lookup Flowfield from Field Name - )

Table C
Field No.
Fields Postcode ( Lookup Flowfield from Field No. - )

seems that Flow field from Table B can return the value. but from table C is empty?

have any ideas?

thanks,