What you could probably do is add a component to your zoomrowlist display, and set the added object to have focus, that way you can capture events using the added object and pass them through to the zoomrowlist. It's more complicated, but it should take care of the issue? Since zoomrowlist had focus by default though, you should be using an observver to determine what item in which row has highlighhtfocus to update the decoration instead of hacking in workarounds like this?
ie
<group id="mygroup">
<zoomrowlist><zoomrowlist>
<poster></poster>
</group>
m.mygroup=findnode("mygroup")
m.mygroup.getchild(1).setfocus(true)