Site offline (but still allow access to front end only for users.)

Hi,

I’m using the plugin “Site Offline or Coming Soon” by wpecommerce. this works great, and Administrators can access the front-end and Dashboard.

I want to allow some (registered users) to be able to access just the front end whilst the site remains offline, but I don’t want to give them access to the Dashboard.

Any ideas on the best way to do this? Thanks!