Force write of Double Select data

I am using MSSQL. I have some business logic on a table that doesn’t allow a certain setting if there is specific data in a related table. The related table is maintained as a Double Select in my Form that maintains the main table.

My problem is that the UPDATE on the main table is performed before the INSERT/DELETE on the Double Select field - so the update failes.

Is there any way to force the Insert/Delete on the Double Select table before the update of the main table?