EasyLanguage, store open at exact time

[twinx]

Hello,

e.g. I want to do a calculation with the open of the bar at 13:00.
I am beginner...

This don't work:

variables: openStart(0), closeEnd(0) ;
if Time = 1300 then openStart = Open ;
if Time = 1700 then closeEnd = Close ;
plot3(closeEnd - openStart ) ;


plot3 shows me for every bar a across or point in my subchart and I can not refer/understand what the values are.
So how can I calculate only the specific bars?

 

[twinx]

Now I see that I have the problem to grab the Open at my bar at e.g. 13:00 a clock!

How can it be done with easylanguage, only receive the open from the bar at e.g. 13:00 a clock?

Thanks