I am trying to update a table from a duplicate query but I keep geeting an error message
The update contains an iff statement

Could you give more information such as what the error message is?

A find duplicates query is only updateable if the underlying table contains a unique identifier which is defined as the primary key. If your table has none, you can temporarily add an autonumber that you define as the primary key. This will allow you to choose one or more of the duplicate rows to delete or update. Without the unique key, Access would have no idea how to match one of the "identical" rows in your find dups query back to a physical record in the table so that it could be deleted/updated. Hence, the need for a unqiue identifier for each row.