Menu navigation

I'm coming back to using IQAN Design after a long period of no exposure to it.  Currently I'm trying to implement a menu navigation system using external buttons (digital inputs).  

The menus can be thought of as being in a circle - as the 'right' button is pressed the screens navigate around the circle to the 'right', wrapping around from the 'last' screen back to the first in the circle - same when going left.  I implemented this a long time ago on another project but for the life of me I can't remember how I did it.  

I've tried using Event Counters, and Integer math, but I can't get the logic to wrap bi-directionally. The Integer function isn't retaining the counter values, and the Event Counters can only reset in one direction, if that makes sense.   I know this should be easy, but my lack of recent experience isn't helping!  Can someone suggest a way of implementing this?

NB - I usually use QCode