Hi Mate,
As far as I know there is no standard programmatic way of querying the GPU load. That said, Google search will reveal some in-official methods on how to do this via hidden Microsoft APIs (use these at own risk). Also note that the GPU load reported with such interface will likely not take info account GPU load of fixed function GPU video codec components.
If you need to tool that reports complete GPU load of Intel processors the check out the Intel Graphics Performance Analyzer (GPA) tool. Unfortunately the tools does not provide a programmatic interface to retrieve this metric.
The above statements are in the context of Windows 7 or Windows 8 Desktop mode.
For Metro you will find lots of additional restrictions that may make it hard to realize your application. Keep in mind that all dependentDLLs must be contained in your application Metro package.
Regards,
Petter