Bods update records issue

target requirement is that only records with column fksaf <> C should come into the target.

some old fksaf = C records are there in the target already. Now the business wants new fksaf = C records should not be seen in the target.

But values for fksaf like 'A', ' ' etc everything should come in the target and records with fksaf = C, once they are changed to A in the source, only then these records should come ?

Kindly Reply ASAP. Its urgent.