Goto everyother frame

Hi All,

I have a Flashbanner with 2 frames. Each frame contains a differnt static jpg.
My boss wants that each time a new user comes to the site,either gotoAndPlay frame1 or frame2. but has to alter everytime. eg. user1 frame1, user2 frame2, user3 frame1…

Is it possible?

I have created random frame, but thats not what I am after.

Many thanx