I would like to use while iterator using Simulink with the structure below, can anyone please help me?

%constant

thi=900;

tci=300;

%initial value

tho=473;

convergence=1;

while convergence>0.1

   qex=1.2*(thi-tho);

tco=(qex/1.3)+tci;

qev=1.2*(tco-tci);

convergence=abs(qex-qev)

tho=thi-(qev/1.2)

end