Michele,
The plugin is not really designed for that – BUT, I personally use a plugin called Ultimate Coming Soon Page. It allows you to do exactly what you are asking about.
What you do, is set up the plugin, then create a Coming Soon type message that everyone else sees. But if you login and are an admin (you can set the level of use), you get to see everything so you can develop the site without prying eyes. I also use it on all of my development sites where I test code (i.e., http://webtestingsite.com/ – everyone gets a message, but when I am logged in, I get to see everything).
One thing to remember – make sure you check the box in WordPress Settings (settings/reading) to Discourage search engines from indexing this site. If you don’t, they will index all the Coming Soon page and it will show up in the Search results.
Best of Luck.
Don
