How to get from a set of initial conditions, to a set of repeatable while loop functions.

Several questions in one here!

I am trying to write a lap simulator. I have a series of equations that needed to be processed to get a range of initial conditions (initial speed etc). I now need to iterate the same series of equations in time steps of 0.001s in order to get constantly updating values (as the vehicle travels down a straight). How do i get a loop to read these initial values, but then create itself a log of the constantly updating values to use for the next iteration?

I am using a while loop (probably with incorrect coding grammar) as a repeat loop would be perfect, but is unavailiable.

This is where I am;

while true
  if Vn > Gear4max
    TractiveForce = TracForce5;
  elseif Vn > Gear3max 
    TractiveForce = TracForce4;
  elseif Vn > Gear2max 
    TractiveForce = TracForce3;
  elseif Vn > Gear1max 
    TractiveForce = TracForce2;
  elseif Vn < Gear1min 
    TractiveForce = TracForce1;
  end
  if TractiveForce > (MuAcc*Downforce0*Mg)
    An = ((MuAcc*(Mdistrear*Mg+Mdistrear*Downforce0-Drag0-RR))/Mg)*9.81;
  elseif  TractiveForce < (MuAcc*Downforce0*Mg)
    An = ((TractiveForce-Drag0-RR)/Mg)*9.81;
  end
  Vn = Vn+(An*Tstep);
  Sn = Sn +(Vn*Tstep)+(0.5*An*Tstep^2);
  Tn = Tn + Tstep;
  Downforcen = CLA*Vn^2;
  Dragn = CDA*Vn^2;
  if Sn > 500
    break;
  end
end

Secondly, how can I put an upper limit on the value of Vn, for example. It is limited through gearing to a certain speed, how can I make it recognize that?

Thank you for all help :)