Forms :: How To Check Table Handlers Correctly

I have a block based on a view. The view is a join on 2 tables, the first table always brings back 4 records for each parameter passed to it in the where clause. The second table is outer joined to the first table and may contain no matched records or some matched records. In some cases there will be a 1:1 match to the first table.

The problem is how to create the table handler procedure correctly. I need to update 2 tables in the table handler procedure.

The block is only enabled for update (to preserve the 4 rows), however some values on the block correspond to values from the second table. When you update a row in the block, how do you know if you are actually inserting a row into the second table or updating an already existing record on the 2nd table.