As per RokuNB's suggestion
I added a keyhandler node to a postergrid to successfully intercept clicks. However using this posterGrid in a panelset and seeing a bug; after navigating to the postergrid the keyhandler is initialized and given focus, then navigating back left to the list, then back right to the posterGrid, the panelSet doesn't slide as it should until further navigation in the grid, and the first cell doesn't seem to have focus (clicking OK does nothing).
If the keyhandler isn't given focus, then all works as it should. But after the keyhandler is given focus, it retains focus even though the panelSet focus has gone to the left list.
I've tried all kinds of things to address this bug,
1) observing focusedchild and trying to set focus on the right panel at the right time.
2) destroying the keyhandler when its parent grid loses focus and re-creating it when it gains focus.
So far nothing works. And I'm wondering if this is actually a bug with panelset, since the keyhandler is returning false, why does panelset care that it had focus? Any ideas to resolve this?