Number of events under a contour color

Is it possible to know the number of events that sit inside the grey line of a contour as in the attached graph?

You can get some inspiration from $ROOTSYS/tutorials/hist/FirstContour.C
-You pick the TGraph contour of your choice
-You make a TCutG object with this TGraph
-You loop on the x,y bins and count the bins that are inside the cut