procedure TForm1.Chart1MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
Var
tmpX,tmpYouble;
yv,xv:double;
code:integer;
begin
if Button=mbLeft then
With Chart1.Series[0] do
begin
GetCursorValues(tmpX,tmpY); { <-- get values under mouse cursor }
xv:=0;
yv:=0;
val(GetHorizAxis.LabelValue(tmpX),xv,code);
if round(xv)<=LastValueIndex then yv:=YValue[round(xv)];