How do I assign a signal value to a variable after a block?

In other words:

I've got a model that gives an output Vs(t), so to speak a simulated voltage as a function of time. I'd like to compare this voltage Vs(t) with the real voltage Vr(t) every single moment, and obtain the error in that instant "E(t)". I want to use this error to change the next voltage Vs'(t+1), in order to reduce the difference between Vs(t+1) and Vr(t+1).

FOR INSTANCE:

Vs(1)= 50, Vr(1)= 42 => The error will be E(1)= 8; The coefficient: 42/50=0.84

If I don't take into the account this error, this will be as big as before in the next second: Vs(2)=49, Vr(2)=40

However, if I give a feed back to Vs(t+1) with the error obtained in t: Vs'(2)= 49*0.84 = 41.16, Vr(2)= 40 => The errors decreases up to 1.16 instead of 9, however, as I don't want to modify the output Vs(t) from the model, the error E(2) used for Vs(3) will be: 49-40= 9; 40/49=0.82

Vs'(3)= 47*0.82=38.54, Vr(3)=38 => The error decreases to 0.54 instead of 9.

And so on...., THEREFORE, I DON'T WANT TO MODIFY NEITHER Vs(t) NOR Vr(t), BUT TO GET A NEW OUTPUT Vs'(t) = Vs(t)*Vr(t-1)/Vs(t-1)

This is what I have:

- Vr(t): output from a block "table from workspace" in which there are 2 columns (the first one is the time and the second the Vreal)

- Vs(t): output from a model

How can I do this?

Help me out please! THANK YOU IN ADVANCE