Set Password to access Dropbox app on Mac??

I use the Dropbox app on my Mac. It sits in the top toolbar (little open box icon). The only problem is that there is no password option or password key like there is on a iPhone. Is there a way to set a password so the app can not just be opened w/o a password?

...and Yes, i know the first post is going to be make a guest account on your Mac and let people use that so they can not access Dropbox... and then the 2nd post will be when you are not at your mac, lock it... well that can all be said for the iPhone and everyone sets a Dropbox password on their phone. (you can just lock your phone too).