I'm not sure of this, but I think the only way is to try to intercept the ZigBee commands that are sent from the Hue Dimmer. But as far as I know HomeGenie doesn't support ZigBee (And Philips Hue use only the ZigBee Light Link protocol)
You could try polling the Bridge from HomeGenie, but as you don't want to flood the network there will be a delay between pressing the switch and HomeGenie receiving the command.
It would be easier just to get a zwave wall switch, it costs a bit more but you'll have better integration with HG.