Matlab - Simulink for cycle

How can I make simulation cycle in Simulink (started by command from matlab) with Fast Restart mode enabled with changing input parameters in Matlab before starting the simulation? - I need to set up just one variable from matlab before simulation, and after the simulation get 4 variables out

[Janko Mrkva]

for(i=1:10)
  sim(model)
  A=A/2;     %variable I need to get to simulink
  i=i+1;
end