A & B Button trapping - roPosterScreen

How can I trap the A & B buttons on a screen? I have tried both the roPosterScreen and the roParagraphScreen and neither of them seem to trap it. I get events for other buttons on the remote with the following line, but never get A or B.

print "Event - msg = "; msg.GetMessage() " | index = "; msg.GetIndex()

I think you would need to get access to the special Roku Gaming SDK to address those individually.

Thanks. I decided to just use * 5 times instead.