>On an app is there any way of checking that any tables/database is open/being used.....I'm writing a back-up procedure and need to ensure all users are out of the system before the back-up starts.

Try opening the table yourself exclusively. If you can, then noone else is using the table.

Then while you have the file exclusively open, copy the data. To retrieve a consistent copy of all the tables, open them all exclusively first before copying any data.