Problem with closeloop of network Narx

Hi, i have a problem with network Narx. i undestand the first steps but i want iterate 3 times with close loop and i don`t the code for this action. The code that i use is:

xlsread p %inputs% xlsread t %targets%

p1=p' t1=t' %transpose the data%

inputSeries=tonndata(p1,true,false) targetSeries=tonndata(t1,true,false)

%create the network" net=narxnet(1:2,1:2,16)

%preparets%

[x,xi,ai,t]=preparets(net,inputSeries,{},targetSeries)

%train network%

net=train(net,x,t,xi,ai)

%simulate%

[y,xf,af]=sim(net,x,xi,ai)

%now I want to iterate three times to value one day after using closeloop% %I do not know how to do it or how it should be the code%

netc=closeloop(net)

[xc,xic,aic,tc]=preparets(netc,y,{},{}) ????

here should get the simulated outputs above, for an iteration but do not know how to be this function (preparets) because I have not the targets in the future. Welcome clarification of the concept . Many thanks