Is is possible to use a netgear wireless router to share a cable internet connection between an airport express and a Sony BD player?

What you are basically attempting to do is extend the Belkin router with the AirPort Express Base Station (AX) via a wireless connection between them. This method is known as a Wireless Distribution System (WDS). Unfortunately, WDS is not a standard and router manufacturers implemented, in most part, to only work with their products ... so it will be very unlikely that you can create a WDS between your Belkin and the AX. There have been a few Belkin model that have been updated by third-party firmware that support WDS, but the models you listed are not any of them.

Ok, thank for clarifying that for me. Then the other option when the routers are interconnected by Ethernet, is to reconfigure the AX as a bridge. This will allow the Belkin to continue to provide both NAT & DHCP services for network clients connected to either router and still allow the AX to provide the wireless network.