If the data doesn't make it to the database, the Update will throw an exception.
If you want to double make sure, one trick is to create an Identity Specification column in which the SQL server will automatically create a unique number. In the table you have in your VB code, that column will be set to a negative number after adding the row. Once the update succeeds, the negative number will be replaced by the actual number the server generated. So you can check to see if the number if >= 0 after the update.