RSI condition about Value

[fabiobioware]

I am analyzing a new way to observe the value that was found in the slope of the line at each tick, I treat this value as a difference, if the line is at the current tick at 50 and it changes at the next tick to 65 I consider that there was a difference of 15 so the line went up, two factors are important, first the value (15) and another value which is a positive number so I understand that the line is bigger than in the (tick) previous moment.
if from 50 it changes to 35 I consider that there was a difference of -15 then it shows that the line is down, therefore smaller than the previous moment.

Values ​​are important because I am analyzing how much aggressiveness in the movement of the other pair is being influential in the pair I am trading. This allows me to search in optimizations which values ​​are more attractive to make my entry, which values ​​are more aggressive that can represent a force in the movement of the asset that is correlated.
I do not know if there is a more effective way to check the previous tick and the current tick to make this calculation, if there is, please let me know.