Realtek Digital Output Shared Mode

All my music is played through either WMP (or Media Center) via Realtek SPDIF optical output to my DacMagic. I've recently started experimenting with some hi-res music downloads (24bit, 96kHz) from Linn. The trouble is that I want my PC to output the digital signal being played, whether that be 16bit 44.1 kHz or 24bit 96kHz.

How do I configure my PC Audio/WMP to output the exact signal that's being played via SPDIF, rather than have to change the shared mode bit rates and frequencies to match what's being played. I don't want my PC to upsample, I want to leave that to the DacMagic, e.g. if I set the shared mode settings at 2 channel 24 bit, 96kHz to cater for the Linn downloads, it then sends evrything to the DacMagic at that frequency which means my 16 bit CD rips have been upsampled by the Realtek chip. I'm using Windows 7. Thanks for your help.