How I can modify StopTime with an Inputdlg?

Hello,

I need that the user can select diferent StopTime depends on the system. I create an inputdlg for introduce the value of StopTime that the user wants but how I can do for change the value of StopTime inside setparam('systemname','StopTime',...)

I try to put like a variable.. but it doesn't works...

PART OF PROGRAM:

ParamSimulacio = {'Introdueix el temps total de simulació','Introdueix el temp de mostreig'};

titol = 'Selecció del temps de simulació';

num_linies = 1;

valorsperdefecte = {'0','0'};

cuadredialeg = inputdlg(ParamSimulacio,titol,num_linies,valorsperdefecte);

TempsSimulacio = str2num(cell2mat(cuadredialeg));

Tstop=TempsSimulacio(1,1);

Ti=TempsSimulacio(2,1);

set_param('Tancs_Dades_Reals','StopTime',Tstop,'FixedStep','Ti');

Thanks!