How to get study line coordinates for beginning and end

Hi !
I am trying to get study line coordinates for beginning and end to use these coordinates in formula. But I cant find right function to obtain these values.


this code below doesnt work:

Plot(C, "Price", colorBlack, styleCandle );
su = Study("SU", GetChartID() );


WriteVal( BeginValue( su ));
WriteVal( EndValue( su ));

I just wanted to code something simpler than for example fibonacci extension.

has anybody an idea?