you don't have external data here. External data means data that is taken from an external interfaced system.
You would need to write this info into table CHVW_EXTERN, which does not really make a bigger difference to the existing CHVW.
What you want is a kind of logic that shows the relation between B1 and A1
Can you phrase this logic? Do you store this relation somewhere?
A relation betwen B1 and A1 according to your example is the second character of the batch number. But this is probably just a simplification. So the question is how do you know which component batch relates to what finished goods batch?