Error from comand line

Hi, when Iam using script like:

h = find_system(mdl,'FindAll','on','Name','Positive Arm A');
no_cells = 10;
set(h,'no_cells',num2str(no_cells))

I got error message:

Error using using_IGBT (line 11)
SubSystem block does not have a parameter named 'No_cells'

whats wrong with this script ? the parametr no_cells defined above...

Thanks, Henry