Hi
This might take a few shots to get it to work but what you asked for is this:
You can kick in the backup BIOS by shutting down the PSU from the wall, then hold down your case power button in and then turn on the power supply button, a few seconds later the board will start, shut off the power supply then. Then you can turn on the power supply again and power up the board normally and DualBIOS will kick in.