How to programatically change the "GPU Acceleration" setting to "Auto Select"?

After a silent installation of the 306.81 driver/physx package I need to be able to programatically choose the “Auto Select” setting for the GPU/CPU selection in the NVIDIA Control Panel. On our systems the setting is visible in: “Desktop/NVIDIA Control Panel/3D Settings/Set PhysX Configuration/Select a PhysX Processor” and the choices are “Auto Select”, “GEForce GTX” and “CPU”.

Installing the NVIDIA software (silently) leaves me with “CPU” selected - and I need it to be “Auto Select”.

We already have code that calls both the the nvapi.lib and the dtcfg.dll but I do not see any way to make this setting with either of these API’s. It would be OK if I had to modify a Registry setting (and) I have tried changing your “Global/NVTweak/NvCplPhysxAuto” value to “01” but that did not change what the NVIDIA Control Panel reports.