Add Readyshare access permission/password

Installed a USB hard disk on my EX6200 (which doesn't appear in the drop-down list of products, Netgear!)

Is there any way to set different access permissions and passwords for different users? At the moment there are only 2 options: no security; or access using the EX6200 login (username: admin, password: my password).

Obviously the data needs to be inaccessible to kids' friends who come around and wish to connect their phones; but in protecting the data I don't want to use the EX6200's logon details - have to give the EX6200's logon to people who shouldn't have it, people who only need access to some of the files on the USB disk.

Can I somehow add an extra username/password pair to use for USB disk access?

Can I (shudder) use Windows own disk-access security to change permissions for particular users and groups? Tried that, but the EX6200 won't let me change anything - is there some trick to doing it?

Thanks,

Rob