How do I program iteration using a for loop?

How do I use a for loop for iteration? My code is as follows:

%Analysis of gas turbine solar dish system
m=0.09; %mass flow rate
PR=3; %pressure ratio
eff_comp=0.8; %efficiency of compressor
cpc=1005; %specific heat capacity of cold area
cph=1100; %specific heat capacity of hot area
e=0.85; %effectiveness of heat exchanger

%Compressor
T1=288; 
P1=101325; 
P2=PR*P1;
Ti2=T1*(P2/P1)^(0.4/1.4); %ideal temperature at exit of compressor
T2=T1+(Ti2-T1)/eff_comp;

%Heat exchanger
T5=800; %assumed temperature at turbine exit
Q=e*cpc*(T5-T2);
T6=T5-(Q/(m*cph));
T3=Q/(m*cpc)+T2;

%Receiver
DNI=800;
Adish=39;
eff_rec=0.85;
T4=((DNI*Adish*eff_rec)/(m*cph))+T3;

%Turbine
P3=P2*(1-0.03)*101325*(1+0.05);
P4=P3*(1-0.02);
P5=P1*(1+0.05);
eff_turb=0.85;
T5V=T4-((eff_turb*T4)*(1-(1/(P4/P5))^(0.4/1.4)));

I essentially assume T5, then I eventually work out a verified T5V, and if T5V doesn't equal T5 then I want to use the previously assumed T5 to do all the calculations again until T5=T5V with a error difference of 1. How would I do this?

[Stephen23]

Put the code in a function, then use fminunc.