The advice I gave you, to not bother to create the otherwise empty record until you need to put something else in it, would prevent that because you could test the child table. Do a DCount of records in the child table where the foreign key matches your new value.
However, something else now bothers me A LOT. What you asked STRONGLY sounds like you are making 1-to-1 relationships between this main table and the other tables, because otherwise you wouldn't care about duplicate entries in these secondary tables. While it is perfectly possible to build tables with a 1-to-1 relationship, it is ALMOST always wrong. Like 98%+ of the time, wrong. Among other things, if you don't have one of the two or three exceptional cases to consider, those records - as you described them so far - would violate a "purity of purpose" rule. You have talked about the FK but that INSERT you showed us didn't contain any primary key. So the only identifying value in that table after that insert isn't a PK, it's an FK, and that means that the record cannot be identified at all (by strict consideration of key usage conventions.) I'm sure it seems clear to you, but to me, at least, that record is a ghost with no substance.
The way I see it, these other tables EITHER shouldn't exist AT ALL, or they should not be of the kind where you care about duplicates. Further, if you actually TRIED to build a relationship between your Job table and a "related" table with a 1-to-1 relationship (as is implied by having a unique index), you would potentially run into a case where you could never create a new record in either table if you tried to maintain relational integrity. Do that more than once and you enter into what is called a "deadly embrace."
Before you go off building ANY tables, describe these tables for us in English so we can advise you of proper infrastructure.
And for the record, once you have decided that you actually NEED a record in the "related" table, the "INSERT" method you chose IS one possible starting point to add the record, though by my standards, you would not create that record until you had more than a foreign key to enter into it.