How to make a template class a friend?

template<class T> struct plotvalue : public std::unary_function<T, void>
{
  plotvalue(//GraphHandler& g) : gh(g) {}
  void operator() (T x) {
        if(x.Param_code == 0x00000002) {
                double time = (x.Time - gh.start_time)/60;
                gh.series.AddXY(time, x.Measure_Value);
         }
  }
  GraphHandler& gh;
};
//---------------------------------------------------------------------------
class GraphHandler {
        friend template<class T> struct plotvalue : public std::unary_function<T, void>
        public:
                GraphHandler(TCustomSeries& s, TChart& c, TChartEditor& ce);
                void plot(MessageHandler& mh, TCustomSeries* series);
        private:
                bool first_time;
                TCustomSeries& series;
                TChart& chart;
                TChartEditor& chartEditor;
                unsigned __int32 start_time;
};

because this dose't work? Or is it even possible?