MQL 5: Comparing two EMA`s values from two points in time


Hello All,

I`m a new member and I`m busy creating an EA, that is able to determine the slope of the EMA in between the opening and the closing of a candle /bar.

To do so, I was thinking to just subtract both EMA`s values. 

After doing some research, I`m wondering if it is even possible, to link a value in an Array position, to a certain point in time.

If so could anyone please explain to me, how I could do this? Or maybe there is a better way of doing this?

Many thanks!