Since LabVIEW still does not have true window even detection, you would have to rig something up. You can make a transparent picture control that can be used to detect mouse clicks or movement anywhere on it, but if the picture control were covering other controls, the user wouldn't be able to use them. I guess you can put the picture controls beneath anything the user needs to use and then monitor the picture control and any control on top of it for signs of use, but its a hastle. You might also be able to use the windows utility VI's to some good use,
http://zone.ni.com/devzone/devzoneweb.nsf/opendoc?openagent&74DDE683A1AFF6988625683A000C0D73&cat=034E59A8530E09DF862568900018707A
