WinStationShadow API Function

[Remko]

Sorry for writing in English, I can read and write some German but its not sufficient to describe my question.
I'm looking for any info on how to use the WinStationShadow function from Winsta.dll to incorporate an option to shadow a users sessions from my app. Currently I use shadow.exe with commandline params but this isn't really nice.
Both tsadmin.exe and shadow.exe seem to use winsta.dll functions WinStationShadow and WinStationShadowStop which presumably use 2 structures _WinStationShadowTarget and/or _WinStationShadowTargetSetup.